“Top Down” predator controls of ecosystem processes:

Can coyotes (Canis latrans) dampen prey population cycles and influence herbivory

rates on the Sevilleta NWR?

Robert R. Parmenter, Lucina Hernandez, and John Laundre

Department of Biology, University of New Mexico,

and Instituto de Ecologia, Durango, Mexico

Estimating coyote impacts on small mammal prey:

• Need coyote density estimates

• Need coyote energy requirements and prey energy equivalences, coupled with digestive assimilation efficiencies

• Need small mammal prey density estimates

• Need coyote diet composition data

• Need estimates of prey productivity

Coyote Density Estimation• Statistics derived from basin-and-range

topographic regions of shrub-steppe in Utah.

• Absolute densities (D=N/A) calculated from 8 coyote populations enumerated during radio-collar studies (i.e., known numbers of coyotes, N, and known home range sizes, A).

• Verified coyote enumeration using radioactive markers in scats.

(Data from Dr. F. F. Knowlton and colleagues, Utah State University)

Development of Scat Index

• Collected coyote scats along measured lengths of dirt roads on valley flats.

• First, cleared roads of scats, then resampled at a later date (several days to a week).

• Scat Index computed as # scats per 24-hour period per mile of road.• Index then correlated with known coyote

density in same area at same time.

Relationship of Coyote Density and Scat Index

Y = 11.42X + 2.66

r2 = 0.97

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Coyote Density (No./Sq. Mile)

Sca

t Ind

ex (N

o./M

ile-D

ay)X

100

Coyote Densities, SNWR McKenzie Flats

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

W S W S W S W S W S W S W S W S W S W S W S

Sampling Periods, 1992-2002

Dens

ity (N

o./S

q. K

m.)

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Coyote Densities, SNWR McKenzie Flats

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

W S W S W S W S W S W S W S W S W S W S W S

Sampling Periods, 1992-2002

Dens

ity (N

o./S

q. K

m.)

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Relationship of Coyote Density and Scat Index

Y = 11.42X + 2.66

r2 = 0.97

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Coyote Density (No./Sq. Mile)

Sca

t Ind

ex (N

o./M

ile-D

ay)X

100

Relationship of Coyote Density and Scat Index

Y = 11.42X + 2.66

r2 = 0.97

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Coyote Density (No./Sq. Mile)

Sca

t Ind

ex (N

o./M

ile-D

ay)X

100 Mean

Summer Density

Relationship of Coyote Density and Scat Index

Y = 11.42X + 2.66

r2 = 0.97

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Coyote Density (No./Sq. Mile)

Sca

t Ind

ex (N

o./M

ile-D

ay)X

100 Mean

Summer Density

MeanFall/WinterDensity

Coyote Energy Budget

B a sa l M e ta b o lic R a te(a t re s t)

A c tiv ity M e ta b o lic R a te(fo ra g in g , te rrito ry d e fe n se)

R e pro d uc tion(p re gn a n cy, la c ta tio n )

T o ta l E n e rg y D em a nd

Daily Coyote Energy Estimates (adapted from Laundre & Hernandez, [ms. submitted 2002])

Component Male Female

• Body Mass: 11.4 kg 9.4 kg

• BMR+AMR Requirement: 1,112 kcal 922 kcal

• Reproduction – Gestation (60 days): 86 kcal

• Reproduction – Lactation (30 days): 1,441 kcal

• Extra pup food (60 days): 541 kcal 541 kcal

Total Annual Energy Demand: 438,340 417,380

kcal/yr kcal/yr

Annual Coyote Prey RequirementsPrey Species Male Female

Lepus californicus 207 199

Neotoma spp. 1,362 1,309

Dipodomys spectabilis 2,848 2,737

Dipodomys ordii 5,697 5,474

Dipodomys merriami 6,962 6,690

Peromyscus/Onychomys spp. 14,242 13,685

Reithrodontomys spp. 20,888 20,071

Perognathus flavus 28,483 27,370

Daily Coyote Prey Requirements

Prey Species # Required/day

Lepus californicus 0.6

Neotoma spp. 3.7

Dipodomys spectabilis 7.6

Dipodomys ordii 15.3

Dipodomys merriami 18.7

Perom./Onych. spp. 38.3

Reithrodontomys spp. 56.1

Perognathus flavus 76.5

Rodent Densities, 5-Points Grassland

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Den

sity

(No.

/Sq.

Km

.)

Dipodomys spectabilis Dipodomys merriami Dipodomys ordii

Perognathus flavus Neotoma albigula Neotoma micropus

Onychomys arenicola Reithrodontomys megalotis Peromyscus truei

Peromyscus eremicus Peromyscus leucopus Peromyscus boylii

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Rabbit Densities, SNWR McKenzie Flats

0

10

20

30

40

50

60

W S W S W S W S W S W S W S W S W S W S W S

Sampling Periods, 1992-2002

Dens

ity (N

o./S

q. K

m.)

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Daily Summer Coyote Prey Requirements(shown on a per sq. km basis)

Daily # Mean # # Days forPrey Species Required Available Depletion L. californicus 0.18 19 106Neotoma spp. 1.11 7 7D. spectabilis 2.29 86 38D. ordii 4.61 115 25D. merriami 5.64 6 1Perom./Ony. spp. 11.55 31 3Reithro. spp. 16.91 2 1Perog. flavus 23.07 424 19

Daily Fall/Wtr Coyote Prey Requirements(shown on a per sq. km basis)

Daily # Mean # # Days forPrey Species Required Available Depletion L. californicus 0.79 19 24Neotoma spp. 4.86 7 2D. spectabilis 9.97 86 9D. ordii 20.08 115 6D. merriami 24.54 6 1Perom./Ony. spp. 50.27 31 1Reithro. spp. 73.63 2 1Perog. flavus 100.40 424 5

Density (Rodents + Rabbits)

0

1000

2000

3000

4000

Den

sity

(N

o./

Sq

. K

m.)

Dipodomys spectabilis Dipodomys merriamiDipodomys ordii Perognathus flavusNeotoma albigula Neotoma micropusOnychomys arenicola Reithrodontomys megalotisPeromyscus truei Peromyscus eremicusPeromyscus leucopus Peromyscus boyliiLepus californicus

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Coyote Diet Composition

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Die

t C

om

po

siti

on

(%

)

Rabbits Rodents Arthropods Ungulates Birds Reptiles Cattle Other Plants

W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Density (Rodents + Rabbits)

0

1000

2000

3000

4000

Den

sity

(N

o./

Sq

. K

m.)

Dipodomys spectabilis Dipodomys merriamiDipodomys ordii Perognathus flavusNeotoma albigula Neotoma micropusOnychomys arenicola Reithrodontomys megalotisPeromyscus truei Peromyscus eremicusPeromyscus leucopus Peromyscus boyliiLepus californicus

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Live Biomass (Rodents + Rabbits)

0

40000

80000

120000

160000

Bio

mas

s (G

ram

s/S

q. K

m.)

Dipodomys spectabilis = 110 g Dipodomys merriami = 45 gDipodomys ordii = 55 g Perognathus flavus = 11 gNeotoma albigula = 215 g Neotoma micropus = 250 gOnychomys arenicola = 25 g Reithrodontomys megalotis = 15gPeromyscus truei = 24 g Peromyscus eremicus = 20 gPeromyscus leucopus = 20 g Peromyscus boylii = 25 gLepus californicus= 2,300 g

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Rabbit Productivity Vs. Predation

0

20

40

60

80

100

120

140

160

Den

sity

(No.

/Sq.

Km

.)

No. rabbits eaten per season Total rabbits available

W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Rabbit Productivity Vs. Predation

0

20

40

60

80

100

120

140

160

Den

sity

(No.

/Sq.

Km

.)

No. rabbits eaten per season Total rabbits available

W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Available = Observed + Est. Reprod.

Rabbit Productivity Vs. Predation

0

20

40

60

80

100

120

140

160

Den

sity

(No.

/Sq.

Km

.)

No. rabbits eaten per season Total rabbits available

W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S S F W S

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Available = Observed + Est. Reprod.Reproduction: 1 litter/season:F-A: 4.5/litter; M-J: 3/litter; A-O: 2/litter, N-J: 1/litter.

Rodent Productivity Vs. Predation

0

2000

4000

6000

8000

10000

12000

Den

sity

(No.

/Sq.

Km

.)

No. rodents eaten per season Total rodents available

S F S F S F S F S F S F S F S F S F S F

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Rodent Productivity Vs. Predation

0

2000

4000

6000

8000

10000

12000

Den

sity

(No.

/Sq.

Km

.)

No. rodents eaten per season Total rodents available

S F S F S F S F S F S F S F S F S F S F

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Availability = Observed + Estimated Reproduction

Rodent Productivity Vs. Predation

0

2000

4000

6000

8000

10000

12000

Den

sity

(No.

/Sq.

Km

.)

No. rodents eaten per season Total rodents available

S F S F S F S F S F S F S F S F S F S F

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Availability = Observed + Estimated Reproduction

Reproduction: 1 litter/6 months,

which doubles population.

Coyote Impacts on Small Mammals:

• At Sevilleta, potential average reduction of rabbit productivity by 46%

• At Sevilleta, potential average reduction of rodent productivity by 32%

• In west Texas, coyote presence resulted in an average ~50% reduction of rabbits and kangaroo rats compared to coyote removal areas (Henke & Bryant 1999)

Tentative Conclusions

• Coyote predation results in substantial removal of prey biomass, prey densities.

• Coyote predation influences small mammal prey population dynamics, but cannot consistently prevent episodic population outbreaks (associated with precipitation dynamics).

• Experimental coyote manipulations needed to verify these calculations.