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Reproduction and Behavior in Captive Idaho and Columbia Basin Pygmy Rabbits

Reproduction and Behavior in Captive Idaho and Columbia Basin Pygmy Rabbits. Becky Elias, Rod Sayler, Lisa Shipley Washington State University. Washington State University Oregon Zoo Northwest Trek Animal Park Washington Department of Fish & Wildlife. Distribution of Pygmy Rabbits .

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Reproduction and Behavior in Captive Idaho and Columbia Basin Pygmy Rabbits

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  1. Reproduction and Behavior in Captive Idaho and Columbia Basin Pygmy Rabbits Becky Elias, Rod Sayler, Lisa Shipley Washington State University

  2. Washington State University • Oregon Zoo • Northwest Trek Animal Park • Washington Department of Fish & Wildlife

  3. Distribution of Pygmy Rabbits

  4. Background • Smallest rabbit in North America • Sagebrush foragers • Dig their own burrow • Columbia Basin (CB) pygmy rabbits listed as endangered

  5. Background • Decline of the Columbia Basin pygmy rabbit linked to: • Loss and fragmentation of deep soil sagebrush-steppe habitat • Predation • Disease • Cattle grazing • Inbreeding depression

  6. Timeline • 1995 – Recovery plan adopted for Columbia Basin (CB) pygmy rabbits • 2001 – Population crash results in an emergency action plan and an emergency listing as endangered. Oregon Zoo (OZ) develops captive breeding protocol using Idaho (ID) pygmy rabbits, and remaining CB rabbits are brought into captivity • 2002 – Captive breeding of CB pygmy rabbits begins at OZ, Washington State University (WSU), and Northwest Trek (NWT) • 2003 – CB pygmy rabbits achieve federal listing as endangered. Beginning of intercross pairings between CB and ID pygmy rabbits

  7. Outline • Breeding behavior • Reproductive success • Nest building • Gestation, birth, and lactation • Weights & Diet • Mortality & survival • Management implications

  8. Breeding • Wilde (1978) and Fisher (1979) • Breed mid-February to mid-May • Induced ovulators • Gestation period of 39 days • Up to three litters a year • Average litter size of 6 kits • No evidence on kits in burrows; hide at base of sagebrush plants

  9. Diet • 2001 – 2002: Lab Diet (high fiber) /Bunny Basics (timothy hay mix) • 2004 (at WSU only): Purina breeder’s diet (high protein)

  10. Breeding Pens

  11. Large breeding pen

  12. Data Collection • Breeding & Maternal Behaviors • Digital video recorder • Bullet cameras and day/night cameras • Pens open for ~ three days • Recorded chasing, copulation, nest-building, birth, and lactation • Reproductive Success • Female counted as pregnant when she built a natal nest • All kits found, no matter what age, used for reproductive success

  13. Results

  14. Breeding Behavior • Male or female initiated chases • Lasted seconds to several minutes • Copulation while chasing or female stopped and allowed male to mount • Brief copulation

  15. Breeding Behavior

  16. Reproductive Success of Females • ID significantly higher than CB on all categories

  17. Reproductive Success of Males • ID significantly higher than CB on all except siring litters (small sample size?)

  18. Reproductive Success • ID and Cross significantly higher than CB

  19. Why is CB reproduction low? • Problem with males, females, or both? • Males: problem with copulation? • Females: physiological - ovulation, behavior – aggression before successful copulation? • Hybrid studies

  20. Possible Answers • Captivity • Problems breeding in captivity • Behavior • Sending/receiving proper behavioral cues • Weights • Underweight animals do not produce effectively • CB males have produced better since the introduction of the higher protein diet • Potential Inbreeding Depression • Decreased mating activity • Longer time before first litter • Increased litter failure • Low sperm count/failed ovulation

  21. Gestation, Birth, and Lactation

  22. Nest Building • 13 days post-conception • Dig separate burrow; 16.5 – 35.5 cm • Use hay to make nest • Pluck fur from abdomen and line nest shortly before birth

  23. Gestation • Gestation period • CB: 22.6 days (n=2)ID: 24.0 days (n=9) p=0.03 • Cause of difference • CB litters born premature • Genetic drift & non-adaptive variation; adaptive variation; inbreeding depression

  24. Birth • 2 morning, 4 afternoon, 3 night • Female plucked fur from her abdomen, cleaning, and opening burrow • At burrow entrance • 14.8 minutes • Covers burrow entrance

  25. Kits • Eyes closed • Little fur • Gray to black skin • Pink bellies • ~15 grams

  26. Lactation • Open once or twice a day to nurse • Kits come to the surface to nurse, with female sitting at the burrow entrance • 10.6 minutes • Recovers burrow • Night (6pm-11pm) • Morning (5am-9am)

  27. Lactation • No apparent correlation between number of nursings per day and litter size, time of year, or health of litter

  28. Emerge 15 days after birth • Female doesn’t cover burrow • Sporadic nursing for several weeks • CB: 3.7 kits Cross: 4.1 kits ID: 3.5 kits • 2 – 6 kits/ litter • Max litters/year: • 3 in small pens, 4 in our large pen

  29. CB: March 5th and May 8th ID: *March 1st and May 25th Cross: February 21st and May 23rd Breeding Season Earliest & Latest successful copulation

  30. Kit Mortality

  31. Adult Mortality

  32. Kit Weights

  33. Adult Weights • CB males and females same weight as ID before breeding season • CB males (-32g) and females (-24g) lost weight.ID males (+11g) and females (+27g) gained weight • New data: both males and females fed the higher protein diet, gained weight (19g for males, and 17g for females)

  34. Large pen weights • At 26 weeks (near adult weight), animals in the large pen weigh much more than animals in the small pens • Males • Large pen: 523g • Small pen: 424g • Females • Large pen: 590g • Small pen: 431g

  35. Captive Population Growth: first 3 years • Growth rate of the CB population was 1.2 during the first 3 years of the study • Projectedpopulation: 60 CB rabbits in 5 years of captive breeding • 10.4% chance of population increasing to 100 and 0.1% chance of crashing to 5

  36. Adult Survival • 2001: 88% • 2002: 56% • 2003: 63% • 2004: 43% • All years: 63%

  37. Kit Survival • 2001: 80% • 2002: 47% • 2003: 59% • 2004: 23% • All years: 52%

  38. Conclusions • Inbreeding • Low reproductive performance • Health problems • Diet • Animals weigh more on a high protein diet • Possibly better reproduction • Population growth • Mediocre at best – long-term viability questionable • Success in any given year is unpredictable

  39. Management Implications • NO Columbia Basin rabbits have been found in the wild since 2001 – may be extinct • Must control disease • Explore reproductive limitations and potential • Increase genetic diversity • Intercross rabbits to maintain unique CB alleles

  40. QUESTIONS?

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