Does immunocontraception in feral horses (Equus caballus) extend reproductive cycling beyond the normal breeding season?

Transcription

1 Iowa State University From the SelectedWorks of Cassandra M.V. Nuñez 2012 Does immunocontraception in feral horses (Equus caballus) extend reproductive cycling beyond the normal breeding season? Cassandra M.V. Nuñez, Virginia Polytechnic Institute and State University James S. Adelman, Virginia Polytechnic Institute and State University Daniel I. Rubenstein, Princeton University Available at:

2 Does immunocontraception in feral horses (Equus caballus) extend reproductive cycling beyond the normal breeding season? Cassandra M. Nuñez*, James S. Adelman*, Daniel I.Rubenstein *Virginia Polytechnic Institute and State University Princeton University Photo by Sue Stuska

3 Number of births Before contraception Non-recipients Recipients 0 MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Month

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7 Ovulatory cycling Reproductive cycling in mares Uncontracepted female pregnancy Breeding Non-breeding Time

8 Traditional forms of contraception

9 Ovulatory cycling Reproductive cycling in mares Uncontracepted female pregnancy Breeding Non-breeding Time

10 Ovulatory cycling Reproductive cycling in mares Uncontracepted female Traditional contraception pregnancy Breeding Non-breeding Time

11 Immunocontraception Porcine zona pellucida (PZP)

12 Ovulatory cycling Reproductive cycling in mares Uncontracepted female Traditional contraception pregnancy Breeding Non-breeding Time

13 Ovulatory cycling Reproductive cycling in mares Uncontracepted female Traditional contraception PZP contraception pregnancy? Breeding Non-breeding Time

14 Shackleford Banks, North Carolina Cape Lookout National Seashore, National Park Service PZP contraception and foal removals

15 Wild horse behavior Harem groups Harem male, females, offspring Stable, long lasting Bodily condition Parasite load Offspring mortality Non-territorial

16 PZP and behavior On few populations During the breeding season Without true controls Powell 1999, Kirkpatrick and Turner 1991, Kirkpatrick, Turner et al. 1996, Kirkpatrick, Turner et al. 1997

17 Contracepted (n=22); Control (n=8) December February 2006 Photo by Doug Schooley

18 Number of group changes Number of groups visited Photo by Doug Schooley

19 Mean +- 1 SE Total group changes Mean +- 1 SE Total groups visited Number of group changes Number of groups visited control contracept Contraceptive status control contracept Contraceptive status Generalized Linear Model; F 2,27 = 6.73, P = PZP treatment, t = 2.11, P = 0.04 Generalized Linear Model; F 2,27 = 6.83, P = PZP treatment, t = 2.42, P = 0.02

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21 Mean +- 1 SE Instances of reproductive interest Reproductive interest 1 Generalized Linear Model; F 1,28 = 9.69, P = PZP treatment, t = 2.26, P = control contracept Contraceptive status

22 Ovulatory cycling Reproductive cycling in mares Uncontracepted female Traditional contraception PZP contraception pregnancy Breeding Non-breeding Time

23 Ovulatory cycling Extended reproductive cycling? Uncontracepted female Traditional contraception PZP contraception pregnancy Breeding Non-breeding Time

24 Foaling date as a proxy for reproductive cycling Nuñez, C.M.V., J.S. Adelman, and D.I. Rubenstein. PLoS ONE, 2010 Number of births Gestation lasts months Conception can be reliably estimated from foals birth date Birth dates of foals born before and after contraception management Before contraception Before Non-recipients contraception Recipients Fligner-Killeen Test for Homogeneity of Variances: Median Chi Square = 12.58, P = Linear Mixed Effects Model: estimate = 1.98, t = 5.51, P < MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Month

25 Birth dates and PZP applications Month of birth Linear Mixed Effects Model: estimate = 0.83, SE = 0.23, t = 3.64, r 2 = 0.65, P = Consecutive PZP applications Photo by Sue Stuska

26 Potential consequences Fall births

27 Potential consequences Male contests Behavioral change in harem males due to behavioral changes in females Physiological changes in harem males ( cortisol and/or testosterone) Photo by Sue Stuska

28 Potential consequences Group changes Cortisol (ng/g feces) zero 0 one 1 two 2 three 3 Number of group changes Cortisol (ng/g feces) v Before During After Time period Dusty Slug Wallace Zelda Carrot

29 Photo by Sue Stuska Thank you Carolyn Mason, Foundation for Shackleford Horses Susan Stuska, National Park Service Margaret Kearns Jessica Smith IWEC organizers

30 Questions?