ECOLOGY OF GHARIAL (Gavialis gangeticus) IN NATIONAL CHAMBAL SANCTUARY

DISSERTATION SUBMITTED IN PARTIAL FULFILMENT FOR THE DEGREE OF

^niin of $t|ilos(optip IN

WILDLIFE SCIENCE

BY

SYED AINUb HUSSAIN

CENTRE OF WILDLIFE & ORNITHOLOGY ALIGARH MUSLIM UNIVERSITY

ALIGARH, INDIA

1 9 9 1

0 ;.pn 139^

DS2168

CENTRE FOR WILDLIFE AND ORNITHOLOGY ALIGARH MUSLIM UNIVERSITY, ALIGARH-202 002

DR. A. H. MUSAVI Professor and Chairman

CERTIFICATE

This is to certify that Mr. S. A. Hussain has carried out this work under my supervision since 1987. This M. Phil thesis entitled "ECOLOGY OF GHARIAL IN NATIONAL CHAMBAL SANCTUARY' is an original piece of work and has not been submitted for any other degree of any other University.

Dated: \(, ./D 9} A. H. MUSAVI

WILDLIFE INSTITUTE OF INDU NEW FOREST, DEHRA DUN-248 006

B. C. CHOUDHURY Scientist SD Project Supervisor

CERTIFICATE

This is to certify that Mr. S. A. Hussain has carried out this work since 1987, through the project "Ecology of aquatic mammals in National Chambal anctuary" of this Institute. This M. Phil thesis entitled "ECOLOGY OF GHARIAL IN THE NATIONAL CHAMBAL SANCTUARY' is an original piece of work carried out through this institute.

Dated: |L | ( |o |^ | B.C.CHOUDHURY

CONTENTS

Frefacc i

Acknowledgement n

Li.st of tables iv

List of figures vi

1. INTRODUCTION 1

Origin 2

Distribution 2

Historical overview 2

Aim of the study 4

Study area 4

History of the Gharial population in the study area 7

Brief biology of the species 8

2. POPULATION STUDY 10

Introduction 11

Methods H

Result and discussion 12

Present Status of Gharial in Chambal River 12

Size composition 14

Difference in expected and observed number of gharial 17

Adult sex ratio 20

3. REPRODUCTIVE SUCCESS AND HATCHLING SURVIVAL 26

Introduction 27

Methods 27

Result and discussion 28

Total number of nest 28

Clutch size 28

Fertility 28

Egg loss 31

Pre-hatching mortality 33

Hatching Success 33

Post-hatching mortality 34

Post-monsoon recruitment of hatchlings 34

4. HABITAT SELECTION 36

Introduction 37

Methods 37

Result and discussion 39

Selection of basking sites 39

Preference for river depth by different size class 41

5. REFERENCES 45

6. APPENDICES 51

PREFACE

This dissertation summarises the result of field study carried out on the ecology

of Gangetic gharial {Gavialis gangeticus) in National Chambal Sanctuary between March

1987 to March 1990. It contains four chapters. Each chapter has three sections which

include brief introduction, methodology adopted for data collection, results and

discussion.

Chapter-I introduces gharial, study area, its climate, history of the gharial population

in the sanctuary and the management input provided for the conservation of gharial.

Chapter-II deals with gharial population study and summarises the results of the two

monitoring surveys carried out in the 425 km.stretch of the Chambal river during 1988

and 1990. This chapter includes present status, densities, population structure and

changes in population trend of gharial.

Chapter-Ill deals with the nesting study and summarises nest monitoring results

between 1987 to 1989. It includes number of nest, nesting density, number of eggs

produced, hatching success and natural recruitment to the population.

Chapter-IV deals with the habitat selection by gharial with special reference to basking

site selection and water depth preference by different size class of gharial along the study

area.

ACKNOWLEDGEMENTS

The present study on the 'Ecology of gharial in the National Chambal Sanctuary'

was funded by the Wildlife Institute of India through the project "Ecology of Aquatic

Mammals in National Chambal Sanctuary". I express my deep sense of gratitude to Mr.

H. S. Panwar, Director, Wildlife Institute of India, for providing logistic and technical

support for this study.

I have deep sense of appreciation for my supervisor Prof, A. H. Musavi,

Chairman, Centre for Wildlife and Ornithology, Aligarh Muslim University, for not only

introducing me to wildlife but also for his guidance and inspiration throughout this study.

I am extremely grateful to my project supervisor. Mr. B. C. Choudhury, Scientist

SD, Wildlife Institute of India, for providing me basic training in crocodile management

techniques, introducing me to wetland research and for his guidance throughout this

study.

I am highly indebted to Dr. L. A. K. Singh, Research Officer, Similipal Tiger

Reserve for his guidance, help and for providing insight relevant to the ecological study

on gharial in Chambal river during the initial period of this study.

I would like to thank Dr. R. J. Rao, Lecturer, Jiwaji University, Gwalior, who

introduced me to Chambal, helped me in field work and shared the hardships with me

in the field.

I gratefully acknowledge the help, encouragement and suggestions given by many

faculty members of my Institute specially Mr. S. K. Mukherjee, Dr. A. J. T. Johnsingh,

Mr. V. B. Sawarkar, Mr. Kishore Rao, Dr. P. K. Mathur, Dr. Ajith Kumar, Dr. S. N.

Prasad and Dr. Shusant Choudhury. Indeed I am grateful to Dr. Ajith for helping me

in statistical analysis and for providing valuable suggestions.

I take this opportunity to thank CCFs(WL) of Madhya Pradesh, Uttar Pradesh

and Rajasthan Forest Department for permitting me to work in National Chambal

sanctuary. I wish to thank Mr. C. M. Vyas, Project Officer, National Chambal Sanctuary

for providing facilities and assistance* during the field work. Also I would like to thank

Mr. S. S. Sajwan and Mr. A. B. Pandey, Range Officer(s) for their time to time help and

assistance during my stay in the Deori Gharial Rearing Centre. Thanks are also due to

Dr. R. K. Sharma, Research Assistant, National Chambal sanctuary for his help in many

ways specially during the field surveys.

Many people helped me in field during this study but Sh. Sukhdev, Sh. Vijay

Singh, Sh. A. B.Pandey, Sh. Brijratan, Sh. Shyam Singh, Sh. Brijraman, Sh. Ramesh and

Sh. Sharmanlal of Madhya Pradesh forest department deserve special mention.

I would like to express my sincere thanks to Dr. A. R. Rahmani, Reader, Center

for Wildlife and ornithology, A. M. U. for reviewing this dissertation and giving valuable

comments. Thanks is also due to Mr. Saeed Ahmad, Chief Librarian, Wadia Institute

of Himalayan Geology for proof reading this report.

I am very grateful to my friends Afif, Jamal, Raghunandan, Ruchi, Parikshit, Nita,

Quamar, Parag, Raghuram, Vijaya Kumar, Chiranjeev, Salim, Ramveer and Imran for

providing me assistance in various ways.

I have no words to express my thanks for the unconditional help and assistance

provided by Mr. Rajesh Thapa and his team viz. Mr. Manoj Agarwal, Mr. Navneet

Gupta and Mr. Lekhnath Sharma on the computer without which this report would have

never been completed. I am indeed, grateful to Mr. V. Sukumar for producing this

report through DTP. Also I am thankful to Ms Asha Jain for Art work at various stages.

I gratefully acknowledge the help and assistance of the villagers along the

Chambal river who provided me food and shelter during my need. Their affection for

me is unforgettable.

Last but not the least I take this opportunity to thank my parents, brothers and

sisters and friends from far and near who wrote me hundreds of inspiring letters and

added charm to my lonely life in Chambal.

HI

LIST OF TABLES

1. Table 2.1 Number and percentage frequency of different size class of gharials

sighted during 1988 and 1990 survey along the Chambal river between Pali (km.

0) and Panchnada (km. 425). 15

2. Table 22 Summarised results of the expected and the actual number of gharial

sightings during 1985,1988 and 1990 along the 425 km stretch of the Chambal

River between Pali and Panchnada. All calculations have been made assuming

that no mortality occurred at any stage.The mean of 1988 and 1990 data has been

considered here. The 1985 census figure has been taken from Singh (1985) for

comparison. 19

3. Table 2.3 Number and density/R.km of gharials along the three zones of the 425

km. stretch of the Chambal river between Pali (km. 0) and Panchnada

(km.425). 22

4. Table 2.4 The average annual exponential rate of increase in density for different

size class of gharials in different zones along the 425 km. stretch of the Chambal

river between Pali (km. 0) and Panchnada (km. 425). 24

5. Table 3.1 Total number of nests and egg to hatchling survivorship during 1987-

1990 along the 425 km stretch of the Chambal river between Pali (km.O) and

Panchnada (km.425). 32

6. Table 4.1 Conclusion on preference and/or avoidance of basking site types by

gharial along the 425 km. stretch of the Chambal river between Pali (km. 0) and

Panchnada (km.425). 40

IV

Table 4.2 (A,B,C & D) Conclusion on preference and/or avoidance of mid river

water depth by different size of gharials along the 425 km. stretch of the Chambal

river between Pali (km.O) and panchnada (km.425). 43-44

LIST OF FIGURES

1. Fig 1.1 Chambal river with some of the important tributaries and land marks.

Pali is river km. 0 and Panchnada is at river km, 425. The study area was divided

in to three zones. 6

2. Fig 2.1 Average annual exponential rate of increase (r. p.a) in the number of

gharial in National Chambal Sanctuary between Pali (km.O) and Panchnada

(km.425). 13

3. Fig 2.2 Number and percentage frequency of different size class of gharials seen

during 1988 and 1990 survey along the 425 km stretch of the Chambal river

between Pali (km.O) and Panchnada (km.425). 16

4. Fig 3.1 Map of the Chambal river showing gharial nesting sites within the 425

km. stretch of Chambal river between Pali (km.O) and Panchnada (km. 425). 29

5. Fig 3.2 Recruitment of breeding females in to the adult population. 30

VI

CHAPTER I

INTRODUCTION

ORIGIN

The family crocodilidae is represented by three distinct sub-families; the

crocodilinae, alligatornae and gavialinae (Ross and Magnusson, 1989), Though they

differ considerably in their morphology, they have common origin (Bellairs, 1987). The

members of recent gavialines might have evolved from long snouted eusuchians through

the eocene and oligocene between 65-57 million year ago. From a possible north

African centre of origin the gavialines may have reached Indian Sub-continent in the

east, Europe in the north and North America in the west (Buffelant, 1989). Their

coastal origin explains their geographical distribution along the tertiary sea ways. In

Indian subcontinent skeletal remains of early gavialines were reported from the pliocene

deposits of the Sivalik hills and from the Narmada valley (Sedgwick, 1905). The

gavialine are now extinct in Africa, Europe and North America; still survive in Indian

sub-continent and are represented by genus Gavialis, the only living member of the

group. In its evolutionary trend the living Gavialis has attained a more advanced level

of organization and the greatest specialization in its phyletic line (Hecht and Malone,

1972).

DISTRIBUTION

The gharial (Gavialis gangeticus) (Gmelin) is distributed in the northern parts of

the Indian sub-continent. Its present distribution extends to the Indus, the Ganges, the

Brahmaputra, the Mahanadi, the Irrawady and the Kaladan river system of Pakistan,

India, Nepal, Bangladesh, Bhutan, and Burma (Smith, 1939; Wermuth, 1953; Neil,

1971; Ross and Magnusson, 1989). The details of its distribution have been discussed

by Singh (1978), Choudhury (1981) and Whitaker (1987).

HISTORICAL OVERVIEW

TTie gharial once common in nineteenth century (Shortt, 1921), was thought to

be on the verge of extinction by 1970's (Bustard, 1980). The factors responsible for the

decline of crocodilians in India were habitat loss and poaching for skin (Daniel, 1970;

Honegger, 1971; Whitaker, 1987), medicine and food (Choudhury and Bustard, 1979)

and also for sport. Besides, the intensification of fishing by nylon nets in rivers also

caused large scale mortalities. Construction of dams and barrages along most of the

river systems altered their habitat. All these factors put much pressure on crocodile

population.

Considering the endangered status of the Indian crocodiles, the Government of

India listed all three Indian crocodiles on Schedule I of the Wildlife (Protection) Act

1972, which banned its killing and trading. In 1973, gharial was listed in Appendbc I &

II of CITES (Groombridge, 1982) which restricted International trade of its skin.

To evaluate the status of Indian crocodilian, surveys were carried out between

1970-1976 by Biswas (1970), Whitaker (1974), Bustard (1976) and Whitaker & Daniel

(1978). By mid-1970's the largest wild concentration of gharials were located in a 5-6

km stretch of the Girwa river near Katerniaghat in Uttar Pradesh and in the Chambal

river (Singh, 1978).

With a view to conserve the species and to develop crocodile farming in India,

a captive breeding programme for all three species of crocodiles viz. gharial {Gavialis

gangeticus), mugger (Crocodylus palustris) and salt water crocodile {Crocodylus porosus)

was initiated under the auspices of the FAO/UNDP project (Bustard, 1980). As a part

of this programme, captive reared crocodiles were restocked in protected areas. Since

then crocodile population in the wild has increased considerably and the restocked

population has also started breeding, indicating initial success of the restocking

programme (Singh, 1985; Choudhury & Choudhury, 1986).

However, the effectiveness of the captive bred restocking programme is difficult

to quantify (Whitaker, 1987). Information of direct relevance to management, such as

population dynamics, habitat utilization and carrying capacity of protected areas are

lacking. This hinders effective management oriented decision making which may reverse

the achievement made during the past decade. This study was therefore carried out in

National Chambal Sanctuary between 1987 to 1990 with the following aims.

AIM OF THE STUDY

1) To determine the status of the present population of Gavialis gangeticus and to

monitor its rate of recovery in the Chambal river.

2) To quantify dynamics of hatching success and early survivorship in the wild.

3) To quantify aspects of habitat types to relate with animal abundance in order to

predict habitat suitability.

4) To recommend better management strategies for the improved conservation of

this species in its prime habitat.

STUDY AREA

The Chambal river is a deep fast flowing perennial peninsular river which

originates in the Singar Chouri peak of the Vindhya range in Mhow, Madhya Pradesh

and flows north-east through Rajasthan, Madhya Pradesh and Uttar Pradesh to join the

Yamuna river. Geographically, the Chambal river lies between 25 degree OO'N, 75

degree 40'E to 26 degree 30'N, 79 degree 15'E. It has a catchment area of 22,531 sq.

km. and an average annual discharge of 4913 mill. cu. sec. (Mitra et. al, 1971). In the

National Chambal Sanctuary, the study area of the present work commenced from Pali

and extended up to Chambal-Yamuna confluence (Fig.l).

Geomorphology

Within the Sanctuary the river flows through areas of deeply eroded alluvium

which forms an intricate network of extensive ravines. Rocky rapids, intermittent gravel

bars and large sand banks are characteristics of the Chambal river. There are many

steep banks and bends where water depth exceeds 25 m during summer (Hussain and

Choudhury, 1988). Numerous temporary water courses from narrow ravines incise into

the river.

Climate

The study area experiences a well defined winter, summer and monsoon. Winter

begins in November and continues till March with minimum and maximum temperature

of 2 °C and 25 °C respectively with a low relative humidity (30-40%). During summer

(March-June) the minimum and maximum temperature is 25°C and 46°C respectively.

South-west monsoon sets in by the 2nd or 3rd week of June and continues up to late

September with an annual rainfall of 500-600 mm.

Vegetation

Climate is largely responsible for the natural vegetational pattern of the Chambal

region. The evergreen riparian vegetation is completely absent. The natural vegetation

of the area consists of tropical thorn forest dominated by Acacia spp. A. arabica is

dominant in the cultivated land and A. catechu is dominant in the forested areas.

A. leucophloea and Anegeiosus pendula is fairly common in some parts of the sanctuary.

Azardirachta indica, Ficus religiosa and F. benghalensis are also occasionally seen near

the village areas. Zizyphus nummularia, Capparb aphylla, C. sepiaria and Salvadora

persica and Salvadora decidua are the major shrubs in the sanctuary. Tamarix dioica is

the dominant xerophytic plant along the river bank. The major aquatic vegetation

consists of Hydrilla verticillate, Vallisnaria spirallis, Potomogeton spp., Imperata cylindrica,

Nitella spp., Chara spp. and Zommochelia spp. Recently, under the ravine reclamation

programmes, all the three States involved (Madhya Prades, Uttar Pradesh and

Rajasthan) in the management of the Chambal valley have taken up plantation of

indigenous species in the ravines by aerial sowing.

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HISTORY OF THE GHARIAL POPULATION IN CHAMBAL RIVER

Gharial population before the initiation of restocking programme

History of the gharial population in Chambal river has been described by Singh

(1985). In brief, prior to the initiation of the restocking programme, Singh (1985)

concluded that atleast 107 gharials (30 breeding adults including 9 males, 43 of 1.2-

1.8 m and 34 less than 1.2 m size) were found between Pali (0km) and Panchanada (425

km) during 1978.

Gharial population after the restocking programme

Following the restocking programme, Whitaker and Basu (1980) reported

presence of 40 gharials of all sizes along the Rajasthan stretch of Chambal river. Singh

(1978) reported 6 males, 12 adult females, 15 sub-adults, 16 juveniles and 34 up to two

year size classes from Rajasthan, Madhya Pradesh and Utter Pradesh parts of the

Chambal river. The first systematic survey was carried out by Singh (1985) during 1983-

84 between Rahu Ka Gaon and Panchnada and in 1984-85 between Pali and

Panchanda. He estimated 451 and 605 gharial during 1983-84 and 1984-85, respectively.

In the absence of reliable population data before the initiation of the restocking

programme, Singhs'(1985) estimation of 1978 has been taken as base line gharial

population for future analysis,

Gharial release

Captive reared restocking programme in the Chambal river was initiated in

1979. By 1990 at least 1800 gharials had already been released into the study area

(Appendix I). This has considerably increased gharial population in the Chambal river.

By now some of these released gharials have also started breeding.

Gharial nesting

Choudhury (1981) located 12 and 11 gharial nests in a 130 km. stretch of the

Chambal river between Barauli and Pureini during 1977 and 1978, respectively. Singh

(1985) reported that at least 12-13 females were breeding in 1979. However, by 1985,

Singh (1985) reported around 35 nests between Pali and Panchnada.

BRIEF BIOLOGY OF THE SPECIES

Sexual Maturity

Gharials are slow breeders. Females of above 2.7 m size or 10-12 years of age

and males of 12-13 years of age with a length of 3.5-3.7 m are considered as adults

capable of breeding (Bustard & Maharana, 1982).

Breeding Season

In nature courtship occurs in late January or in the first week of February

(Bustard, 1984). The eggs are laid in late March or early April, which hatch in early

June (Singh, 1978).

Clutch Size

The clutch size of gharial varies considerably. Singh (1978) reported minimum

and maximum clutch size of 10 and 33 respectively, from the Narayani, Kali and

Mahanadi River. Choudhury (1981) reported minimum and maximum clutch sizes of 14

and 61 in 1977 and 14 and 62 in 1978 from the Chambal river. Rao (1988) estimated

mean clutch size as 38.4 from the Chambal river during 1985-87.

Incubation Period

The incubation period varies from 71 to 95 days (Singh 1978). Choudhury (1981)

reported incubation period of 61 to 76 days in simulated nest condition, Rao (1988)

observed mean incubation period of 57 to 68 days from Chambal river. However,

incubation period varies according to temperature.

8

Hatching success

On the basis of his three studies, Singh (1978) reported hatching success to be

12.1 to 31.7%, 15.1 to 71.8% and 22.8 to 100%; and Choudhury (1981) reported it to be

65.4% in 1977 and 66.40% in 1988 from the Chambal river in simulated condition.

GroHth

According to Singh (1978), the annual growth rate during the first year varied

from 332.60 to 536.50 mm while during the second year it varied from 475.50 to 526.00

mm. But Choudhury (1981) reported mean annual growth of 48.73 and 29.90 cm in first

and second years after hatching. All these studies were conducted under captive

conditions.

CHAPTER n

POPULATION STUDY

INTRODUCTION

In order to determine the effectiveness of gharial rehabilitation programme in

Chambal river, it was necessary to monitor the gharial population at regular intervals

(Antoon De Vos, 1982). Continuous monitoring of this rehabilitated population, beside

indicating population trends would also justify the past management inputs and their

success or help in developing fresh management strategy. The following chapter

describes the results of the two monitoring surveys carried out during 1988 and 1990 in

the 425 km. stretch of the Chambal river between Pali (km. 0) and Panchnada (km. 425).

METHODS

The methods used to estimate the gharial population were adopted from Singh

(1985). The study area was divided into three different zones. Zone-I lies between 0

km to 170 km (a rocky stretch with rapids), zone-II lies between 170 to 270 km (with

moderate pools) and zone III is between 270 to 425 km (has many large deep pools).

Total count of basking gharials was made from a 5 m long aluminimum boat

driven by 40 HP Yamaha engine. All counts were made during the month of February-

March coinciding with intensive basking frequency and aggregation of large gharials for

breeding. Usually, 2 or 3 observers were stationed at the front seat of the motor boat,

each searching gharials on either banks with the help of 8 x 40 mm prismatic binoculars.

The motor boat moved at 8-10 km/hour, down mid river. Whenever basking gharials

were seen, their approximate size, basking site topography and mid river water depth

were recorded. If a gharial was seen in water its size was approximated from its snout

length following the methodology adopted by Singh (1981).

The size classes of gharials from 0.60 to 3.0 m were recorded on an increment of

30 cm. Gharials < 0.6 m. were considered as hatchlings and > 0.6 m and < 0.9 m were

considered as yearlings. The next size classes were > 0,9 and < 1,2 ( below release

size); > 1.2 and < 1.5, > 1.5 and < 1.8 (release size); > 1.8 and < 2.1 , > 2.1 and <

11

2.4, > 2.4 and < 2.7 (sub-adult); > 2.7 and < 3.0; and > 3.0 meters (adult).

Differentiation between adult and from female was made by observing the presence of

protrubance of nasal orifice or gliara in male which is lacking in female.

In the absence of any objective study to accurately census gharials in an aquatic

habitat, it is almost impossible to count the exact number of animals in their natural

environment. Most studies particularly on captive gharials have indicated that almost

all animals come out of water to bask when the ambient water temperature becomes

lower than the ambient air temperature. It is, however conceded that there is possibility

of minor error in the population estimation mainly due to the basking behaviour of

juvenile, sub-adult and adult gharials and their preferred basking temperatures.

However, during this study, when repeated surveys were made during November-March

in a sample stretch, a very low standard error was recorded (in prep.). This indicates

that chance of missing a gharial that was not basking during the survey period was very

low. Hence certain assumptions were made for this study, which are:

during the survey period all the gharials present in a given stretch were basking,

all the basking gharials were seen and their sizes were estimated.

RESULTS AND DISCUSSION

Present status

During 1988 and 1990, 820 and 982 gharials were estimated between Pali (km 0)

and Panchanada (km 425) respectively. This shows a crude density of 1.92 gharials/river

km in 1988 and 2.31 gharial/river km in 1990, an increase of 20% within two years.

Comparing these estimations with those of Singh (1985) in 1984-85 an increase of 59%

was recorded in the year 1990.

Pre-stocked population of 1978; and 1985 (Singh, 1985) and present population

of 1988 and 1990 were transformed to natural logarithms and regression analysis was

used to calculate the average annual exponential rates of increase. This shows an

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average increase of 19% per annum (Fig 2.1). The population data for 1984-85, 1988

and 1990 was further analysed by using following formula (Caughley, 1980)

N,= NQC"

Where N, = population in period t; NQ = population in period 0 (initial population);

e = 2.718 (constant); t = time in years; r = rate of increase.

This shows considerable decrease (r = 8%) in the growth rate during this period

i.e between 1985-1990. Beside analysis of growth rate during 1978 and 1984-85 shows

r = 33%, a high growth rate after the initiation of restocking programme.

A glance at the conclusions regarding population size and growth suggests that

the gharial population of Chambal river shot up rapidly following restocking programme

and now it is gradually stabilizing. However, if the present trend of population growth

continues, the population of gharial in Chambal river can be expected to double within

next 8-9 years depending on the rate of restocking programme.

Size composition of gharials

Table 2.1 gives the size class composition of gharial population in the Chambal

river during the two survey periods. Analysis of size class composition of gharial suggests

a decreasing tendency from hatchlings to yearlings in any given year and then again there

is an increase in size classes 3, 4 and 5 due to reintroduction. Then there is a sharp

decline between size class 6-9 (Fig 2.2), which is either due to large scale mortality or

migration into the Yamuna river.

14

SI

No.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

Size class of

gharials

Hatchlings

Yearlings

> 0.9 & <

> 1.2 & <

> 1.5 & <

> 1.8 «fe <

> 2.1 & <

> 2.4 & <

> 2.7 & <

> 3.0 m

1.2 m

1.5 m

1.8 m

2.1 m

2.4 m

2.7 m

3.0 m

1988

Number

89

81

115

187

119

56

38

21

14

100

(male 14)

% Freq.

10.85

9.87

14.02

22.85

14.51

6.82

4.63

2.56

1.70

12.19

1990

Number

74

68

112

218

192

119

59

27

16

97

(male 13)

% Freq.

7.53

6.92

11.40

22.19

19.55

12.11

6.00

2.74

1.62

9.87

Table 2.1 Number and percentage frequency of different size class of gharials sighted

during 1988 and 1990 survey along the Chambal river between Pali (km 0)

and Panchnada (km 425).

15

PERCENTAGE FREQUENCY

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Difference in expected and observed number of gharial

In order to determine the difference in expected and observed number of gharial

(not seen/lost) during the survey, four sets of population data viz 1978 population

(population before the initiation of restocking prograimne); data that was collected by

Singh (1985) during 1984-85; and the data of present study collected during 1988 and

1990 were taken in to consideration. For each data set following Parameters were taken

in to account for analysis:

PARAMETERS VALUE & SOURCE

Rate of natural recruitment of hatchlings

Per annum growth rate of hatchlings

till 1.2 m size

The number of gharial restocked per year

1985 = 6.5%, 1986 = 6.5% Singh (1985)

1987-1989 present study (Chap-III)

30 cm (assumption, 35-47 cm in

captivity)

Uttar Pradesh Forest Deptt. Appendix-1

Subsequent per annum growth rate of wild

and restocked gharial following release

Minimum size of adults

15 cm (assumption; 16 cm/annum in

captivity; Bustard and Maharana, 1982)

> 2.7 m (Hornaday, 1885; Singh, 1985)

In the study area the monsoon sets in within three to four weeks after hatching

of gharial eggs. Hatchling mortality is substantial and occurs mainly during this first

monsoon. The egg to post monsoon survivorship of hatchlings has been discussed in

Chapter-Ill. For the present discussion the number of hatchlings that survived the first

monsoon or of one year old has been excluded.

17

i) difference in one to two years of age

Table 2.2 indicates an expected 7 and 8 percent (X = 7.5%) loss or mortality

between hatchling to yearlings ( > 0.6 & < 0.9 m size) during 1988 and 1990

respectively i.e. if 100 hatchlings were observed in a survey year (Y), one may expect 92.5

yearlings in the next year survey (Y2). The expected loss in hatchling-to-yearling class

between consecutive year survey is due to the mortality/migration or due to the

differential growth rate among hatchlings (Singh 1985). Possibility of missing some

hatchlings during the survey can not be ruled out.

ii) difference in two to three years of age

Simultaneously, during 1988 and 1990 an expected 40.24 and 25.84 percent

(X = 33.02) gain in the number of juvenile > 0.9 & < 1.2 m were estimated

respectively. However the gain in the subsequent size class i.e > 9.0 & < 1.2 m is either

due to the differential growth or due to emigration.

iii) difference in three to four years of age

Subsequently in the next category i.e from >1.2m and <1.5m size, an expected

5.64 percent gain and 6 percent loss was estimated during 1988 and 1990 respectively.

Such variation in the expected value was due to the differential or the stunted growth

in some of the re-stocked gharial. Singh (1985) has predicted 8cm/annum growth rate

of restocked gharial in the first year.

iv) difference in four to five years of age and/or following restocking

Among the size class > 1.5m and < 1.8m a sharp increase in the loss of gharial

was expected (X = 66%). This is because majority of gharials of >1.2m and <1.5m size

were restocked gharial and there may be many factors which are responsible for the

large scale loss of these gharials. But the following factors enhance chances of loss;

18

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a) natural mortality following release in wild particularly during monsoon.

Singh (1985) reported possible natural mortalities among displaced (from captivity

to wild) gharial but such mortality was never reported from the study area. However

Blake and Lx)veridge (1975) have recorded a mortality up to 62.3 percent among Nile

crocodile when the release size was Im.

b) migration of the released stock out of the sanctuary limit during monsoon.

It appears that majority of the restocked gharial move out of the sanctuary limits

as far as 600-800 km away from the release site (Singh, 1985 with pers. com with Shyam

Lai, 1981). The restocked gharial within the first year of release, not being acclimatized

to monsoon, go out of the sanctuary limits. This accounts for the large scale loss of

gharial of this size class.

v) difference in five to nine years of age

The mean expected loss of gharial between five to nine years of age was uniform

(28.28%) with a standard error of + 6.5 percent. However, slight rise in the expected

loss was found during 5-6 and 7-8 years of age i.e. 33.75 and 33.50 percent respectively.

The reason for this is that, following release the survivorship in subsequent years

gradually increases except at 7-8 years. The gharials of this age group (7-8 years) are

being sub-adult face intense competition with the conspecifics. As there was no report

of mortality in this group, it is believed that about 33% of this size class of gharial (sub-

adult) also move out of the sanctuary limits.

Adult sex ratio

Data collected during 1987-90 indicates adult male to female ratio of 1:7, while

Singh (1985) reported it to be 1:4 during 1984-85. This ratio however pertains to the

entire 425 km stretch of the study area and is the overall average of all nesting sites.

The maximum number of females associated with a male were found to be 13 in one

20

nesting site near Nadigaon (km 65) (Fig 3.2), As observed adult sex ratio was found to

change due to the poaching of males. Gharials are polygamous. Male casualties

adversely affect the nesting activity and also intensifies mating competition among

females.

Change in population trend

Two sets of population data have been taken into consideration here; that

collected by Singh during 1984-85 and that obtained in the present study during 1988 and

1990. Both the data were pooled together to form four following categories (Table 2.2);

< 120 cm Juvenile

> 120 cm & < 180 cm Juvenile 1

> 180 cm & < 270 cm Sub-adult

> 270 cm Adult

The density of animals of each size class in each study zone (Table 2.3) were

converted in to their natural logarithms and then separately regressed with monitoring

years using SPSS Programme on a personal computer to calculate the average annual

exponential rate of increase (r/annum) in the density of each category. The result

indicates different r/annum. in different zones among different size-classes Table 2.4.

Assuming that there was no change in habitat condition during 1984-90 and

expecting an uniform rate of increase in the density of each size class in each zone, the

trend in population change in the study area has been discussed.

In zone-I, there was a positive increase in the density of size class-1, 2 & 4 and

decrease in density of size class-3. The increase in density of size class-1 is due to the

increase in number of nest in zone-I (Append. II) which have increased the recruitment

of size class-I from the wild. The increase may also be due to the immigration of

hatchlings and yearlings from upstream between Kota barrage and Pali (Fig 1.1).

21

Zones Years Size class of gharials

<1.2 <1.8 <2.7 >2.7

No. Den. No. Den. No. Den. No. Den.

1

1

1

2

2

2

3

3

3

1985*

1988

1990

1985*

1988

1990

1985*

1988

1990

20

40

65

105

164

102

51

81

87

0.11

0.23

0.38

1.05

1.64

1.02

0.32

0.52

0.56

54

60

61

86

91

111

58

155

238

0.31

0.35

0.35

0.86

0.91

1.11

0.37

1.00

1.53

55

42

55

55

40

52

68

33

98

0.32

0.24

0.32

0.55

0.40

0.52

0.43

0.21

0.63

23

56

63

18

44

36

12

14

14

0.13

0.32

0.37

0.18

0.44

0.36

0.07

0.09

0.09

* 1985 Data is taken from Singh (1985) for comparison

Table 2.3 Number and density/river km. of gharials along the three zones of the 425 km

stretch of the Chambal river between Pali (km.O) and Panchnada (km 425).

22

Singh (1985) has reported that nesting occurs in this stretch also. Increase in size class-4

was due to the reintroduction programme between 1982-85. The reintroduced gharials

appear to have joined the breeding group during 1989-90. The marginal increase in the

density of size class-3 (release class) was probably due to the slack in reintroduction

programme in this zone between 1985-90 and also due to the migration of this size class

to zone-II and III.

In zone-II, while there was positive increase in the density of size class-2 and 4,

there was considerable decrease in the density of size class-1 and an asymptote in size

class-3. The increase in size class-4 was due to the reintroduction effort in this zone

between 1980-85. However, the 6% increase among size class-2 in this zone may be due

to the emigration from zone-I. Singh (1985) has designated this size class as wanderers

as they have a tendency to move very long distances. The 6% increase in the density of

size class-2 in this zone corresponds to the decrease in the same size class in zone-I,

indicating continuous migration of size class-2 or the release class into the zone-II.

The introduction in this zone was discontinued after 1985 and hence the decrease

among size class-3 was found. This also indicates that the individuals of size class-2 who

migrate into this zone from upstream do not settle there and it is possible that they

migrate in to the zone-Ill. Inspite of the increase of number of nests in zone-II, the rate

of increase in the density of size class-1 in this zone was negative. Zone-II being easily

approachable and in close proximity to the field camps of Madhya Pradesh and Utter

Pradesh Forest departments, most of the eggs for captive rearing are being collected

from this zone which reduces the natural recruitment rate from wild. The recent

increase in egg predation (Chapter III) might also be a cause of decrease in the density

in this zone. Migration of this class into the zone-Ill during monsoon may be another

reason for the negative growth rate in this zone.

23

Size class of gharial

r p.a. R2 N Significance growth

Zone I

size class 1 size class 2 size class 3 size class 4

0.3099 0.0303 0 0.2614

0.9881 0.7500 0 0.8818

3 3 3 3

0.0695 0.3333 1.0000 0.2516

30 3 0

26

Zone II

size class 1 size class 2 size class 3 size class 4

0.0725 0.0638 0.0140 0.1732

0.00296 0.90625 0.02722 0.56120

3 3 3 3

0.9653 0.1981 0.8945 0.4706

-7 6

-1 17

Zone III

size class 1 size class 2 size class 3 size class 4

Zone wise

0.13990 0.35488 0.09548 0.06283

0.8475 0.9491 0.1172 0.7500

3 3 3 3

0.2555 0.1448 0.7775 0.3333

13 35 9 6

Zone I Zone II Zone III

0.1419 0.0327 0.2106

0.9998 0.2749 0.9996

3 3 3

0.0244 0.6486 0.0114

14 3

21

Table 2.4 The average annual exponential rate of increase (r/annum) in density for different size class of gharials in different zones along the 425 km stretch of the Chambal river between Pali (km 0) and Panchnada (km 425).

24

In zone-Ill, the rate of increase in the density for all the size classes was positive.

The high rate of increase among size class-1 appears to be due to the increase in the

number of nests as well as due to the emigration of haichlings and yearlings from zone-II

and I. The high rate of increase in size class-2 seems to be due to the recent

intensification of the reintroduction programme. Considering the low rate of increase

in size class-3 and 4, the increase among size class-1 and 2 was high. If the hatchlings

and yearlings from the wild and the release classes are settling in this zone, we may

expect an increasing trend in the density of size class 3 and 4 in subsequent monitoring

years.

The average annual exponential rate of increase in the density of total population

of gharial in zone-I, II and III was 14, 3 and 21 percent respectively suggesting that the

population in zone II is gradually stabilizing and there is still some scope in zone-I and

III for more gharials.

25

CHAPTER ra

REPRODUCTIVE SUCCESS AND HATCHLING SURVIVAL

26

INTRODUCTION

The effectiveness of crocodile restocking programme are determined either by

continuous monitoring of the restocked population or by monitoring the nesting efforts

made by the restocked population. In the previous chapter the present status and

change in population trend of gharial in the sanctuary have been described. In this

chapter information on the trend in nesting effort, reproductive success, hatchling

survival and the factors which govern the rate of natural recruitment to the population

have been objectively discussed. This study was conducted between 1987 to 1989 and

it contains nest monitoring data from the 425 km stretch of the study area.

METHODS

During the nesting season (March-April) pre-identified nesting sites were visited

regularly and the nests were searched with the staff of the National Chambal Sanctuary.

Nests were located by following gharial tracks or by probing the suspected nest locations

by a metal poker; a practice usually employed by the management staff. If and when a

nest was found, the eggs damaged by probing were removed. All eggs were counted

without disturbing their orientation. The unfertilized eggs were identified, as those

which did not form an opaque spot or band (Web et al, 1983a, 1983b). Information on

nest predation, harvest, hatching, pre and post hatching mortality was collected by

checking nesting sites regularly or from management staff employed for safeguarding the

nests. As nesting sites were spread over the entire 425 km study stretch, it was not

possible to check all the nesting sites. Information only on the total number of nests was

later confirmed after post hatching survey or from the field staff of the forest

department.

Data on the hatchling survival was collected by conducting winter surveys in the

entire 425 km study stretch as described in chapter II.

27

RESULTS AND DISCUSSION

Number of nests

A total of 45, 52 and 57 nests were located in 1987, 1988, and 1989 respectively

in the 425 km stretch between Pali and Panchnada (Appendix II). The total number of

nests between 1985 and 1989 were converted into their natural logarithms and were

regressed against year to calculate the average annual exponential increase in nesting.

This suggests an increase of approximately 13% per annum (Fig. 3.1). However, during

1987-89, 28 percent increase in the number of nest was observed (Fig 3.2). This also

indicates an approximate of 13.5% per annum increase in the recruitment of breeding

females in to the population. If the present trend continues the total nesting effort by

gharial population along the Chambal River will double within the next 4-5 years,

assuming that the restocking rate will be uniform.

Clutch Size

No significant variation in mean clutch size was found during the study period

(Table 3.1). However, the increase in mean clutch size during 1988 may be due to the

large sample size. Comparison of present clutch size with the data collected in 1977-

1978 by Choudhury (1981) suggests a significant decrease in the clutch size. This may

be due to the younger breeding female with smaller clutch size joining the breeding

group. In case of reptiles the young females produces smaller clutch size while older

females produce larger clutch size.

Fertility

A percentage of apparently infertile eggs is a feature of most reptiles which

deposit large clutches (Bustard, 1982). In our study the ratio of fertile to infertile eggs

was fairly constant (Table 3.1). Comparing the present study with that of Singh (1978)

and Bustard (1981) the present fertility rate in gharial along the Chambal river is high.

28

-1 1 r r

1085 1986 1987 1988 1S89

YEAR Fig.3.1. Average annual exponential rate of increase Cr -P-o) '" the

number of gharlal's nests In the National Chombal Sonet, between Pali (km 0) and Panchnada. Rate of Increase was calculated by regression analysis using SPSS Programme in a PC/AT. Conflation -Q987B9 R^O.07593 Sig. -0.0016 Slop* (S.EL) =0,13157 (r.p.a)

c T3 d) d)

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1 -Q. *-^ .E 0)

:z; :3 g ^ a; ;H

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o c

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O) c • • D O 0) . X)

o *— c

F • • -» • —

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u.

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00 0)

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^ (U n E 3 c

;z; <D cfl -1-^

During this study a complete infertile clutch (clutch size = 5) was also recorded in 1988,

where as 100% fertile clutch has also been found during this study. Considering the

male to female ratio of adult gharials in communal nesting sites, it seems that one male

can successfully serve about 13 females.

Egg loss

i) Egg Damage in the course of nest searching

Around 3.5% of the eggs are being damaged every year in the course of nest

searching by the traditional method employed by the forest department to locate the

nests. Throughout the study period such losses were common (Table 3.1). Considering

the endangered status of gharial, to reduce the egg loss it is suggested that instead of

protecting the individual nests the nesting sites should be protected.

ii) Damage caused during handling of eggs

During the study period it was observed that a significant number of eggs did not

hatch (Table 3.1). This may be due to several reasons;

a) disturbance leading to change in natural orientation of the eggs at early stage which

causes embryo mortality.

b) healthy eggs spoilt by the damaged eggs left inside the nest.

Loss due to the former reason has happened in Bagadia sand (km 26) during 1987

and in Baroli (km 58) during 1989 and by latter in Bharra (km 130) during 1988 where

four entire clutches did not hatch.

iii) Egg loss due to predation

Inspite of protection measures, incidence of nest predation showed an increasing

trend between 1987 to 1989. It could not be ascertained if this was due to density

dependant predation or due to some other factors. Choudhury (1981) identified jackal

31

Parameters

TotJil no.of nests Mean dutch size

Total no.of eggs estimated as

Number of eggs collected

Eggs damaged

Unfertile

Fertile

Eggs predated

Not hatched

Pre-halching mortality

Total egg loss

Hatching success

Number of Hatchlings produced

Post Hatching mortality

Hatchling survival

Egg to Hatchling survivorship

1987-88

45 36.2 n = 34

jt6.59

1629

288

63 (3.8%)

113 (6.93%)

1516 (93.07%)

96 (5.8%)

41 (2.5%)

4 (0.29%)

317 (19.45%)

1312 (80.54%)

1024

8 (0.36%)

89 (8.75%)

5.46%

1988-89

52 37.38 n=47

_L8.6

1944

472

66 (3.39%)

153 (7.87%)

1791 (93.15%)

109 (5.6%)

175 (9.00%)

46 (2.36%)

549 (28.24%)

1395 (71.75%)

923

15 (0.77%)

NA (7.10%)

NA

1989-90

57 35.8 n=41

JL6.43

2041

306

71 (3.47%)

168 (8.23%)

1873 (91.76%)

384 (18.81%)

48 (2.35%)

6 (0.29%)

677 (33.17%)

1364 (66.82%)

1058

16 (0.78%)

74 7.92%

3.62%

Mean (%)

36.46

1871

66.66 (3.56%)

144 (7.67%)

92.66%

10.07%

4.61%

0.98%

26.95%

73.03%

-

0.68%

4.54%

Table 3.1 Total number of nests and egg to hatchling survivorship during 1987-1990 along the 425

Kin stretch of Chambal river between Pali (Km 0) and Pachnada (Km 425).

32

. -O M II

{Canis lupis), common mongoose (Herpestes edwardsi), bandicoot (Bandicota malabarica)

and ratel {Mellivora capensis) as potential nest predators along Chambal river.

Choudhury and Bustard (1979) identified Varanus also as a potential predator of the

eggs of the salt-water crocodile {Crocodylus palustris) in the Andamans. However there

was no evidence of Varanus predating gharial eggs along Chambal river but evidence of

nest predation by jackal was common. During 1987 evidence of nest predation by ratel

was also recorded from Baroli. Considering the significant losses particularly in 1989 it

seems necessary to investigate and identify specific causes and to take more effective

measures for the protection of eggs.

Pre-hatching mortality

In 0.98% of eggs, embryos developed fully but hatching did not occur. It appears that

during incubation some unknown environmental factors influence hatching rate. In 1988

the percentage of pre-hatching mortality was quite high (Table 3.1). In Papripura (km

216) and Barenda (km 245) 50% and 100% mortality respectively, was observed. This

may be due to the very low humidity of the nest substrate. According to Ferguson

(1981) the young ones oi Alligator missisippiensis die of asphyxiation when they fail to

break open the egg-shell hardened due to the dryness of the nest substrate. Sharma

(1990) has also confirmed that gharials egg-shell membrane become tough during the

last stage of incubation. Mortality at these two sites might have occured when the nest

was opened and exposed to sun for a long period at the initial stage which caused loss

of soil moisture leading to large scale mortalities prior to hatching.

Hatching success

During the study period mean hatching success was found to be 73.03%. The

percentage of hatching however decreased considerably since 1987 (Table 3.1). Decrease

in the percentage of hatching was probably due to the mishandling of eggs and egg

33

predation. Besides these, the egg damaged during the nest searching and pre-hatching

mortality due to some unknown environmental factors also influenced hatching rate.

Rao (1988) has estimated 75% hatching from the Baroli nesting site (km 60) in Chambal

river. However, in this study, much difference was not found in the rate of hatching

success.

Post-hatching mortality

As observed the major causes of hatching mortality before the monsoon were

congenital defects and weakness due to some unknown reason. The hatchlings with

congenital disease (Singh and Bustard, 1982) die within a few days after hatching.

Besides some weak hatchlings fail to reach water and die of heat and dehydration. No

hatchling mortality due to predation was observed in course of the study.

During the study period mortality due to congenital axial skeletal defect were

observed in the eggs collected from Baroli nesting site. Mortality caused by incomplete

umbilical constriction and weakness was common at Tighri-Rithoura nesting sites (km

210). The causes of mortality due to bulge-belly and weakness were seen in other

nesting sites also.

The pre-monsoon hatchling mortality during the study period was uniform

(Table 3.1). Singh and Bustard, 1982 did not find any congenital defects in hatchlings

from the eggs laid along the Chambal river during their study in 1979 and 1981. This

suggests that the occurrence of congenital defects in hatchlings along the Chambal river

is a recent phenomenon.

Post-monsoon recruitment of hatchlings to the population

The post-monsoon recruitment of hatchlings to the population during 1987-88 and

1989-90 was estimated as 8.69% and 6.99% respectively. This indicates that during

monsoon around 92% hatchlings migrate out of the sanctuary or die. Subsequent

34

analysis of data suggests that the mean natural recruitment from egg to hatchling after

monsoon was only 4.54%. Singh (1985) estimated 6.5% natural recruitment during 1983-

85 in the Chambal river. It appears that the present lower rate is due to the increase

in the percentage of egg loss.

35

CHAPTER - IV

HABITAT SELECTION

INTRODUCTION

There is a paucity of information on habitat selection by ghariai. This study provides

information on the selection of basking and nesting sites an3 preference for river depth

by different size-classes of ghariai as indicated by their differential abundance at the

various locations along the 425 km stretch of the Chambal river between Pali and

Panchnada.

It is difficult to conclude that the selection of basking sites and river depth by ghariai

is merely on one consideration i.e. availability. There may be many other ecological

factors operating simultaneously at the favored sites, which influence selection. But there

was no scope in this study to investigate a host of biotic and abiotic factors and their

significance for ghariai. To understand the real basis of selection far more intensive

studies are necessary. However to satisfy the limited objectives of this study, only a few

abiotic factors such as availability of basking and nesting sites and river depth preference

have been taken into consideration.

METHODS

Because of varying depth and nature of basking sites the availability and the

utilization sampling in a riverine habitat is difficult to quantify. Hence in the present

study the non-mapping technique (Marcunn and Loftsaarden, 1977) was adopted to

quantify the availability of river depth, basking and nesting sites along the study area.

In this case each sampling point has been considered as one habitat unit.

The mid river depth was measured at 426 points, at 1 km apart along the 425 km

stretch of the Chambal river. The depth points, were categorized as follows :

37

category River depth

1 >0.9& < 1.9 m

2 >2.0& < 2.9 m

3 >3.0& < 3.9 m

4 >4.0 & < 4.9 m

5 >5.0 m

Suitable basking sites were identified as done by Rao and Singh (1987) and

categorized into the following three categories:

1) Sandy bank or sand bars

2) Clayey banks

3) Rocky bank, islands and rocky outcrops

As there were 426 sampling points on each of the two banks and 59 mid-river rocky

islands and outcrops, thus a total of 911 points were sampled. At each site, the number

and size of gharials, the nature of the basking sites were recorded within 200 m radius.

Many smaller islands or outcrops within a radius of 200 m of a sample point have been

considered as 1 unit.

Statistical Tests

For the analysis of resources availability and utilization data the confidence interval

technique of Neu et al (1974) was used in conjunction with Chi-square goodness of fit

test. This test was used to determine whether there was a significant difference between

the expected utilization of different depth categories, type of basking site etc. and the

observed frequency of their usage. If a statistically significant difference was found

between the utilization and availability, the data were further investigated by Bonferroni

confidence interval following Byers et al. (1984) to determine which category of habitat

were being preferred.

38

RESULTS AND DISCUSSION

Selection of basking sites

The availability and utilization of basking sites has been quantified in this section.

Table 4.1 gives a summary of the proportionate availability of different basking sites and

the number and percentage of basking gharial observed at each type of sites; and

simultaneous confidence intervals using Bonferroni approach.

The result of the test indicates that sandy portion of the river banks at Sand bars

were frequently utilized by gharial. Comparatively less preference was shown for rocky

bank and rocky out crops. There seems clear avoidance of clayey river banks.

Discussion

Actual observation indicating gharial's preference or avoidance of different basking

sites is a subjective conclusion. Assignment of biological basis of preference and

avoidance is called for. The mechanisms adopted by ectothermic animals for

maintaining the desired level of body temperature differ from those of warm-blooded

animals. Gharials like other crocodilians usually avoid high ambient temperature

(Thermoconformers) (Lang, 1987). Temperature selection (either heat seeking or heat

avoidance) within the available habitats is an important daily activity of all species of

crocodiles. Thus basking in sun during winter and remaining in water most of the time

during summer, as has been observed during the study, is to regulate body temperature

without much expenditure of energy and to facilitate optimum metabolism. Observation

during this study shows that individual gharials have strong attachment to particular

basking sites to which they return again and again when the disturbance is over.

It can therefore be concluded that, the selection of basking sites is influenced by the

following factors:

39

e V

o S o S B

« 8 - .S

td a

X §

v

O 3

o- eg

U 3

A rf

H 3

r-r-I—1 (N O o

r-cs m o\ MD O

in o o

ON i-H

o 00 Ti­es Tt

o

T-H • *

in r m CJ

o Tt in

o T-H

MD

ON

OS

CJ

o

o\

00

00

00

o

I—I

r-ON

CJ

00

ON ON

00 o 00

oo cs

CO

MS r-!

o 00 Tf (N Tj-

o

rH rl-in t-~ fO

o

00 r-ON ON >-H

o

00

u C!

00

o

^ a.

3 ^

a) physical characteristics of the site

Sandy parts of the bank are preferred because it seems that gharials find it

comparatively easier to crawl on sandy surface than on rocky or clayey surfaces.

Another advantage of basking on sandy surface is that it contains far more moisture than

other surfaces and hence it provides a hot (sun) and cool (moisture in sand) environment

thus reducing the chance for desiccation while basking in sun.

b) avoidance of disturbance

Sites free of disturbance appear to be preferred for obvious reasons. In situation

where undisturbed sandy sites are not available, gharial seems to prefer rocky outcrops

as second alternative sites for basking.

c) presence of escape cover

Presence or absence of escape cover near the basking site appears to influence

selection for particular sites for basking. Often basking gharials feel disturbed or

threatened by human beings and whenever it happens they retreat into the water for

safety. For this they need deep water close to the basking site. Gharial therefore seems

to prefer such site that are close to easily accessible escape cover. This conclusion is

also supported by Rao and Singh (1987).

d) camouflage value of the surroundings

Another factor which also seems to influence the selection of basking sites is the

capacity of the site and surroundings to camouflage gharials. At times gharials easily

merge with the sandy back drops and appear like a piece of drift-wood. Even when a

gharial basks on slopy flat rock its colour matches with the dark background (Rao and

Singh, 1987).

River depth preference

Availability of desired or preferred depth at each sampling point and the frequency

of its usage by different size classes of gharial has been objectively described in this

41

section. Tables 4.2 A, B, C and D contain summarised data on the number of basking

gharials at different sites, the proportionate availability of different depth at the sampling

sites; and simultaneous confidence intervals using Bonferroni approach.

The Bonferoni intervals for the size class-I (< 1.2 m) shows that the mid river depth

category 1 and 2 are utilized more than would be expected by chance as compared to

the category 3, 4 and 5 where the degree of utilization is very low (at 0,05 level of

significance).

The depth category 2 appears to have been used by the size-class II (>1.2 m and

< 1.8 m), more than the depth categories 3,4 and 5, while the category 1 has been used

rarely. The difference is too wide to be regarded as a chance phenomenon.

The gharials belonging to size-class III (> 1.8 m < 2.4 m) have been observed to use

the depth category 5 more frequently than the depth category 3 and 4, while the category

1 and 2 were rarely used and here also the difference is too wide to be regarded as

chance phenomenon.

The adult gharials or size class-4 (> 2.7 m) were found to use the depth categories

4 and 5 more frequently than the depth category 2 and 3, while they avoid category 1.

Discussion

While the range of depth variations at different sampling points was 1 to 27 m which

is quite wide (Hussain and Choudhury, 1990), it is difficult to attribute the ecological

basis of the selection of certain depth by gharials. However, some biotic and abiotic

factors affecting the behaviour of gharials are discernible.

Apparently food availability (both quantitative as well as qualitative) and hiding cover

value does differ with depth of water. Young gharials feeding only on small fishes

(fingerlings) will prefer shallow water for foraging as well as for cover. Similarly large

size gharials feeding on larger fishes need deep water both for foraging and cover.

42

V .. w a e ^ a! e

,4} 73

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c5 c5 o o C5

n rH r~ NO r^ O 00 (S t ^ ' - I f< r~- o r>; '-J .-( NO r^ rNj CNJ i-H (S (S i- . <S o o o o c5

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S o r- o (s f s '-H i-H r^

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(S <-( r~~ o fo O 00 (M r- r-H ro r o r~ i-i T-i vo r- (S (N <-! (N fS <-! (N 0 0 0 0 0

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O t^ r* CO O fO fO (N Tj-

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r^ '—I r^ so fo o 00 fs r^ '-H CO r~- o r~- '—I t-i s o r - ( S ( S '-I f S ( S r-H C^ O O O* O' O

o 2; 2 (S o

^ 2 ; : ' = e e e 6 p o o p r 4 CO Tj-' i r ! V V V V 5 d <^c^=a E

< < < D^ Cu

O CO i—I ON (N O s o CO O s o O ON 1—1 T-H O O <N ^ rj- s o O O (N Tt m

o o o d o

O O O CO s o O CO O 00 00 O s o i—I ON (S O O ON r^ ON O O O (N CO

d d o" d d

( S T-H t-^ s o CO o 0 0 (N r~ '-I CO r^ o r~ '-' i-H so r- cs (N 1-1 ( s ( S T-i r s

d d <zi d d

o^ CO ^ o 00

olic 5 5 2 t— ^-' 10 ^ *"

5,; so' 10 fS ^ CO (N

ON

C O '—I "—I <—I C O r j -

CT\ O N ( N r ^ -—I CTs ' - ' CO i ^ r-~ iin CO Tf 00 ^ t-^ P (N ON p ON CO* co' d o \

(N CN f-i --I

cs '-I r~ so CO o 00 ts r- i-i CO r^ o r^ 1—I T-i so r- CM <s <-! (N fS T-i (S d d d d d

.a C/3

CTs >—I I-H T—(

d (N CO •<*' A A A A A

> (A

es

.a

so 2; 2 f^ 0

^ 2 : " = s e e e p p p p r4 CO •*' i n V V V V =«=y = «y E Os <—' >—1 I—' i—'

d (N CO •<*' >n A A A A A

5

_

^ o

t

o

I

a

i s: o

. 0

o

<~N1 • - - I

i O

I 2 o

Q U

H

Hence gharials below 1,2 m size prefer 1-2 m depth, while gharial above 1.2 and

below 1,8 m size prefer 2-3 m depth. On similar consideration the sub-adult and adult

gharials prefer water deeper than 5 m. The range of depth selection by gharial smaller

than 1.8 m is quite wide probably because this group consists mostly of released gharials

who have a tendency to move over long distances (Singh, 1985), Such gharials are more

opportunist; they settle where ever they find less competition. But the adult gharials

prefer deeper water only as it provides sufficient cover for them.

45

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w

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51

APPENDICES

APPENDIX-1 Gharial release locations along the Chambal river and number ofgharial released between 1979-1990. (Sources: Utter Pradesh and Madhya Pradesh Forest Department)

Release site Zone Km. Year No. ofgharial released

Jeora Brenda Kenjara Pureini Kuthiana Chinnoni Sahaspura Baroli Deogarh Nadigaon Baroli Rameashwar Kenjara Keori Deogarh Pureini Pali Pali Barenda Pali Rameshwar Udi Rameshwar Rameshwar Baroli Pinahat Nandgaon Tigra Pinahat Tigra Pinahat Tigra Pinahat

III II II II II I

III I I I I I

III III

I II I I

II I I

III I I I

III III II

III II

III II

III

287 265 297 227 222 145 297 58 165 67 58 22

297 280 165 227

0 0

265 0

22 352 22 22 58

272 320 210 272 210 272 210 272

1979 1980 1980 1980 1981 1981 1981 1981 1982 1982 1982 1982 1983 1983 1983 1983 1984 1984 1985 1985 1985 1986 1986 1987 1987 1987 1987 1988 1988 1988 1989 1990 1990

75 15 45 50 44 83 43 83 45 50 49 43 24 74 50 50 38 30 60 10 20 1

87 48 50 97 42 15

150 5

150 5

150

53

APPENDIX-2 The number ofgharial nesting sites and the number of nest located during 1985-89 in the 425,km stretch of the Chambal river between Pali (km 0) and Panchnada (km 425). (updated over Singh, 1985 and Rao, 1989).

SI No.

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16

Nesting sites Zone km.

Bagadia sand Gobarda Baroli Nadi gaon Banwara Bharra Basaidaang Tigri-Rithoura I Papripura I Pureini I Daljitpura I Barsala I Barenda I Khera II Gyanpura II Kasaua II

TOTAL

I 25 I 35 I 58 I 65 I 115 I 130 I 170 I 210 I 216 I 225 I 235 I 242 I 265 I 358 I 368 I 372

1985

? -

12 1 -

7 -

2 -

11 -

0 0 0 2 2

35

Number of nests 1986

1 1

14 2 1 5 -

6 -

1 -

4 0 0 2

37

1987

2 2 14 3 1 5 -

8 -

2 -

2 3 1 2

45

1988

2 3 10 10 1 5 1 5 1 4 1 2 3 2 2

52

1989

2 3 7 13 1 5 1 7 2 5 0 2 3 2 2

57

54