REPRODUCTIVE PATTERNS

LIFE HISTORY

POPULATION DYNAMICS

Peromyscus

REPRODUCTION

Seasonal patterns (latitude gradient)

ASEASONAL

SEMI-SEASONAL

STRONGLY SEASONAL

Cebus capucinnus

ARGENTINA

Seasonal reproduction in the tropics

Marmosa

REPRODUCTION

Differential response to seasonal environments

Costa Rica – savannah (wet & dry seasons)

(seasonal) (aseasonal)Zygodontomys

Artibeus jamaicensis

WEANING

Seasonal reproduction

Coastal California

RAINDROUGHT

Microtus californicus (grass)

Reithrodontomys megalotis (seeds)

Seasonal reproduction

Haplonycteris fischeri (Philippine pygmy fruit bat)

births are synchronouswithin local populations

Seasonal reproduction

post-implantationdelayed development

6-9 months

Delayed developmentand

Reproductive synchrony

ovulation

birth

implantation

normal development resumes

1 litter per year

Ptenochirus jagori (Philippine fruit bat)

Seasonal reproduction

Delayed developmentand

Reproductive synchrony2 litters per year

up to6 month

delay

Initial asynchrony

Synchrony established

Synchronized births in BOTH age groups

no delay

1 litter per year

Sperm storage and delayed fertilization

Antrozous pallidus (Pallid bat)

SPERM STORAGE IN UTERUS

FERTILIZATIONBIRTH

ACTIVE (SEXES SEGREGATED)

COPULATION

HIB.HIBERNATION

SPERM PRODUCTION

SPERM STORAGE (MALE)

Seasonal delayed implantation(Mustelidae)

Delayed implantation of blastocyst (1 month)

Fertilization

Gestationand birth

Implantation

Delayed implantation of blastocyst (8+ months)

Delay of more than 9 months

Litter size and latitudePeromyscus maniculatus

Reproductive patterns

How many young? How often?

ITEROPARITY -- repeated production of offspring at intervals throughout the life cycle

Mean litter size = 8

Mean litter size = 2

Reproductive patterns

Litter size and elevation

Peromyscus maniculatus

4.0

4.4

5.0

5.6Decreasing season lengthand increasing litter sizewith increasing elevation

The increase in litter size increase with both latitude and elevation reflects the same basic life history trend:

Immediate reproductive expenditure increases with declining probability of future reproduction (in harsh environments where adult survival is low)

SEMELPARITY -- a single act of reproduction duringan organism's lifetime. Also known as:

“BIG-BANG”

Reproductive patterns

What if the likelihood of future reproductiondrops to near zero?

Semelparity is common in plants and invertebrates, but rare in vertebrates

Brown antechinusAntechinus stuartii

Gray short-tailed opossumMonodephis domestica

Didelphidae

Dasyuridae

Northern QuollDasyurus hallucatus

Semelparity in male marsupials Seasonal, promiscuous breeding

Dasyuridae

Males compete for mating opportunities during a very brief mating season

Males fast during mating, and have high levels of androgen and glucocorticoids

Extreme physiological stress

Complete male die-off following mating period

Does NOT apply to females (may live multiple years)

“PARTIAL” SEMELPARITY

26 April 2002

2-year-old male at emergence in his first breeding season

26% loss of massNumerous wounds(died ca. 23 May 2002)

Arctic ground squirrel (Spermophilus paryii)

Seasonal heterotherm (winter torpor)

Intense male-male competition for mates

Promiscuous breeding immediately following emergence

Females breed as yearlingsMales delay reproduction until 2nd spring

Same male 3 weekslater

16 May 2002

Bowhead whale (Balaena mysticetus)

Maturity: 15-25 yearsGestation: 13-14 monthsBirth interval: 3-4 years

Maximum longevity

Longest-lived mammal?

Traditional stone & ivory Inuit harpoon points (from recently killed animals)

Maximum longevity: more than 200 years?

Ornithorhynchus anatinus Duck-billed platypus 17.0

Tachyglossus aculeatus Short-nosed echidna 50.0

Antechinus stuartii (male) Brown antechinus 1.0

Antechinus stuartii (female) Brown antechinus 3.0

Macropus giganteus Eastern gray kangaroo 24.0

Suncus etruscus Savi’s pygmy shrew 2.7

Erinaceus europaeus Eurasian hedgehog 7.0

Pteropus giganteus Flying fox 31.4

Myotis lucifugus Little brown bat 30.0

Callithrix jacchus Common marmoset 16.0

Macaca mulatta Rhesus macaque 36.0

Pan troglodytes Chimpanzee 59.4

Homo sapiens Human 122.5

Gorilla gorilla Gorilla 47.0

Castor fiber European beaver 25.0

Spermophilus sp. Ground squirrel 11.0

Glaucomys sabrinus Northern flying squirrel 13.0

Perognathus longimembris Silky pocket mouse 8.3

Reithrodontomys spp. American harvest mouse 1.5 

Canis lupus Gray wolf 20.0

Panthera leo Lion 25.0

Crocuta crocuta Spotted hyena 40.0

Antilocapra americana Pronghorn 12.0

Hippopotamus amphibius Hippopotamus 49.0

Tursiops truncatus Bottle-nosed dolphin 30.0

Balaena mysticetus Bowhead whale 150+

Maximum longevity

Body size & Longevity

Placentals(excluding bats)

Non-passerine birds

Passerine birds& non-hibernating

bats

Body Size and Life History Traits -- (artiodactyls)

MAXIMUM LIFE SPAN

AG

E A

T M

AT

UR

ITY

LIFESPAN AND AGE AT MATURITY

Body Size and Life History Traits -- (artiodactyls)

Body Size & Length of Gestation(Placentals)

PRECOCIAL

ALTRICIAL

ENTIRE SAMPLE

Body Size

Underlying influence of metabolic rate

Body size & Longevity

Non-passerine birds

Placentals(excluding bats)

Passerine birds& non-hibernating

bats

Hibernating bat species

Insight from heterotherms

3-fold increase

Fasting boosts longevity in animals

Thursday, March 03, 2005 Health 24.com

Fast track to longevityMouse study shows molecular connections between

caloric restriction and lifespan extension

March 7, 2005 The Scientist

THE SEARCH FOR A UNIVERSAL LONGEVITY GENE

October 2004

The Longevity GeneA gene that releases stored fat may be the key to a longer life.

Ornithorhynchus anatinus Duck-billed platypus 17.0

Tachyglossus aculeatus Short-nosed echidna 50.0

Antechinus stuartii (male) Brown antechinus 1.0

Antechinus stuartii (female) Brown antechinus 3.0

Macropus giganteus Eastern gray kangaroo 24.0

Suncus etruscus Savi’s pygmy shrew 2.7

Erinaceus europaeus Eurasian hedgehog 7.0

Pteropus giganteus Flying fox 31.4

Myotis lucifugus Little brown bat 30.0

Callithrix jacchus Common marmoset 16.0

Macaca mulatta Rhesus macaque 36.0

Pan troglodytes Chimpanzee 59.4

Homo sapiens Human 122.5

Gorilla gorilla Gorilla 47.0

Castor fiber European beaver 25.0

Spermophilus sp. Ground squirrel 11.0

Glaucomys sabrinus Northern flying squirrel 13.0

Perognathus longimembris Silky pocket mouse 8.3

Reithrodontomys spp. American harvest mouse 1.5 

Canis lupus Gray wolf 20.0

Panthera leo Lion 25.0

Crocuta crocuta Spotted hyena 40.0

Antilocapra americana Pronghorn 12.0

Hippopotamus amphibius Hippopotamus 49.0

Tursiops truncatus Bottle-nosed dolphin 30.0

Balaena mysticetus Bowhead whale 150+

Maximum longevity

Logistic population growth

Population dynamics

K = carrying capacity

Exponential growth

Population dynamics – logistic growth

Growth determined by r

Growth limited by K

K-selectionSelection for traits favored in stable

environments withpopulations at or near carrying

capacity

large size

few offspring

late maturity, prolonged period of parental care

long life expectancy

individuals may reproduce many times

most individuals live to near the maximum life span

r - selectionSelection for traits favored in unstable

environments that promote rapid population growth when densities are

below carrying capacity

small size

many offspring

early maturity, shortperiod of parental care

short life expectancy

individuals have few opportunities to reproduce

most individuals die within a short time but a few live much longer

r & K selection theory

Sheep(Tasmania)

“K-selected”

Peromyscus

“r-selected”

Population dynamics

Population fluctuations

Ord’s kangaroo rat(Dipodomys ordii)

New Mexico

Multimammate mouse(Mastomys natalensis)

South Africa

Population cycles

Brown lemming(Lemmus sibiricus)

Alaska

Multi-annual “cycles”

Population cycles

Lepus americanus

Lynx canadensis

Predator – prey cycles

Canada (Hudson Bay Co.)