Reproductive Biology / Reproductive Strategies

Factors Influencing Timing of Breeding

Male Reproductive Cycle Testes: Permanently scrotal – primates, canids, felids, ungulates Withdrawn into body seasonally – rodents, insectivores Year-round breeders Long-day breeders Short-day breeders

Female Reproductive Cycle Estrous cycles vs. Menstrual cycles

Ovulation

Reproductive Strategies “Normal Development ” from conception to parturition Delayed Fertilization Delayed Implantation Delayed Development

Breeding Ovulation Fertilization Blastocyst Formation ImplantationParturition Suckling Anestrus Post-partum estrus “Normal Pattern of Breeding and Pregnancy” Embryonic/Fetal Development - Reproductive Tract - Bicornuate

White-tailed deer (Odocoileus virginianus) Copulation Parturition Anestrus Nov./Dec. Mid-late May Total gestation = ~ 200 days Eastern spotted skunk (Spilogale putorius) Long-day breeder Copulation Parturition Anestrus April Late May/June Total gestation = ~ days Short-day breeder

Elk (Cervus elaphus) Estrus October Parturition Mid - June Anestrus (8.5 mo.) (3 - 4 mo.) John Morrison (1960): 17 hr. estrus / 21.2 day estrous cycle Early October / Late October / Mid-November / Early December [August – Nov/Dec][Sept – Dec/Jan]

Delayed Fertilization Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June Spermato- Testes Copula- OvulationViable embryos genesis regress tionFertilizationdevelop depending Implantationupon ambient temperature Sperm Sperm stored in stored in epididymis uterus Gestation 56 – 100 days in length Breeding occurs before hibernation Western Big-eared Bat Corynorhinus townsendii Delayed Development

Delayed Implantation Obligate delayed implantation – Facultative delayed implantation

Black Bear Ursus americanus Foresman and Daniel (1983). Journal of Reproduction and Fertility 68:

Grizzly Bear Blastocyst mm

Black Bear Plasma Proteins PregnantNon-pregnant Molecular Weight Date Protein Molecular Weight Date

Short-tailed weasel Mustela erminea Breeds May – July 10 – 11 mo. Obligate delay Parturition April – May Post-partum estrus Northern fur seal Callorhinus ursinus Breeds 26 June – 5 August 1 Estrus lasting 1 day 3 – 5 mo. Obligate delay Total gestation = ~ 360 days

Facultative Delayed Implantation Estrus Parturition Parturition Breeding Day Post-partum Post-partumestrus 200 day delay due to suckling Resumption in devel. ~ 30 d prior to exit of pouch young 200 day delay 1 23 Red Kangaroo

Eastern Gray Kangaroo Western Gray Kangaroo Red Kangaroo Swamp Wallaby Tammar Wallaby Quokka Seasonal Quiescence Seasonal Anestrus Lactational Quiescence Lactational Anestrus Ovulation Parturition

Swamp Wallaby – Macrotus bicolor Lactational Quiescence Parturition Ovulate, breed and conceive ~ 2 days prior to parturition

Environmental Influence on Reproduction Field observations suggested that short-term fluctuations in temperature and rainfall affect the reproduction of prairie deer mice (Peromyscus maniculatus bairdii); Females exposed to unusally warm spring temperatures had 0.4 more young / litter; female embryos negatively affected; Females exposed to warm temperatures in the autumn had 0.5 fewer young / litter; male embryos negatively affected;

Myers, P.L., L. Master, and R. A. Garrett Ambient temperature and rainfall: an effect on sex ratio and litter size in deer mice. J. Mammal. 66, Field conditions: Noted temperatures on days when field-caught mice were in early pregnancy; If max. temp. fell into the upper 5% of average observed maximums = “HOT” If min. temp. fell into the lower 5% of average observed minimums = “COLD”

Laboratory Conditions and Experimental Design: 1)Paired males and females at age 40 – 60 days and left until successful pregnancy; Removed offspring (female exhibits post-partum estrus); 2)Day of birth of one litter (Day 0) = Day of conception of next litter (Day 23); 3)Exposed females to 12 h of high temperature: 33 – 35 o C; Exposure occurred at either: Day 23 (n = 12)Controls held at 22 – 26 o C Day 21 (n = 26) Day 19 (n = 28) Day 17 (n = 7) Day 15 (n = 12)

Measured: Total number of young Number of male and female offspring Sex ratio of litter Average weight of offspring

Total number young/litter Number of young/litter Implantation Increased female mortality Increased male mortality Decreased litter size Males/ Females

Differential sensitivity of male and female embryos in utero How do you think that this would affect the results of demographic studies?

Nutritional Influence on Reproduction Cheatum, E. L., and C. W. Severinghaus “Variations in fertility of white-tailed deer related to range conditions.” Trans. 15 th N. A. Wildl. Conf. Best range Good range Poor range Poorest range

Moose River De Bar De Bar – heavy harvest (bucks/ does); Moose River – relatively in- accessible; little doe harvest Shaded areas are antlerless deer seasons De Bar – heavy buck/doe harvest; Increased logging; 1943

1939 – 1943 No. Pregnant Does Avg.Young/doe De Bar57.1% 0.71 Moose River90.7% – 1949 De Bar100% 1.78 Moose River68.8% 1.00 Fertility Indices recorded for 911 does: embryo counts/number of corpora lutea as index of ovulations

Conclusions:

Verme, L. J Reproduction studies on penned white-tailed deer. J. Wildl. Mgmt. 29:74-79.

Dietary Group: I – II Excellent diet III Moderate diet IV Poor diet Verme (1965).

McClure, P. A Sex-biased litter reduction in food- restricted wood rats (Neotoma floridana). Science 211, Polygynous mating system No difference in cost to female to produce male or female offspring Mother in poor health should increase investment in female offspring

Bred woodrats Assigned females to control or food-retricted groups Control: Food ad libitum Food restricted: 70 – 90% of maintenance requirement of non-reproductive female Experiment lasted 21 days (normal time to weaning) Experiment Design:

Control litters Restricted litters Parturition

Controls Restricted MFMF MFMF

Conclusions

- Trivers & Willard Hypothesis -

Roe deer:Clutton – Brock; 15 years of data on Roe deer; Coypu (Nutria): Females in good condition abort small litters of predominantly female embryos; - Large litters and small male litters are retained; Possums: Females given more food produce significantly more males 1.4/1.0 M/F; Old females are in poor condition 1.8/1.0 F/M;

Verme, L. J Reproduction studies on penned white-tailed deer. J. Wildl. Mgmt. 29:74-79.

Verme, L. J., and J. J. Ozoga Sex ratio of white-tailed deer and the estrus cycle. J. Wildl. Mgmt.45: Bred does 15 – 95 h after the start of estrus behavior; Ovulation occurs 12 – 14 h after estrus teminates; Hours Post-copulation 13 – – – – 96 % Males: Duration of estrus – hrs Ovulation

Social Contraception

Bruce effect: Pregnancy blockage Whitten effect: Estrous synchronization Lee-Boot effect: Induced estrus

“Pheromone-induced reproductive inhibition in young female Peromyscus leucopus.” Haigh, G. R. et al Biol. Reprod. 33, Ad Male/Juv Female Bedding Floor Adult Male + Juvenile Female White- footed mice (Peromyscus leucopus) All pairs maintained until juvenile female littered, or for 150 days; Clean bedding H 2 O sprayed on bedding Soiled bedding from Ad Female’s cage (direct contact - no floor) Soiled bedding from Ad Female placed under floor (no contact – olfactory) Urine from Ad Female sprayed on bedding (no contact – olfactory) Controls: Experimentals:

M = Adult Maleolf = olfactory (soiled bedding y = juvenile femaleunder floor) cb = clean beddingu = urine (under floor – olfactory) H 2 O = water in contactF = presence of adult female sb = soiled bedding in contactParous = pregnant Nulliparous = non-pregnant

M = Adult male y = juvenile female 0 – 24 = hours of contact with Adult female Parous = pregnant Nulliparous = non-pregnant Delay of reproductive maturation last days.