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Cetacean Birth Control Methods: Data Remains Unclear

As advocates for the scientific management of animas in human care, it is important to discuss the development and maintenance of breeding programs designed in their best interest.  Breeding programs allow for zoological sustainability  and offer hope to protecting species from extinction.

The responsible management of zoological populations provides continued genetic diversity, without depleting or disrupting wild populations.  With the help of scientific research, these programs are very different today compared to the 1960’s when first established.  Breeding programs utilize the combined expertise of veterinary and animal care staff when measuring genetic diversity within viable populations.

The priority is always the safety and well-being of the animal.  Animals in human care are active participants of their own healthcare.  They are trained and conditioned for daily husbandry behaviors through positive reinforcement.  For example, this makes trainers and keepers able to ask the animal to present their tail flukes for a blood draw.  Through this positive conditioning, the animal remains calm during the procedure.  After completion, the animal is reinforced for a job well done.  Rewards vary from favorite foods to special toys and physical stimulation such as a rub-down.

There are various methods of zoological breeding; the first being artificial insemination (AI).  In this method, sperm is collected from a mature male animal.  Using an endoscopy procedure, the genetic material is inseminated in a mature, viable female unrelated to the male (Neto, et al. 2008).  This procedure is not unlike any other trained husbandry behavior.  The AI procedure is typically brief, lasting approximately 30 minutes.  During the procedure, females may or may not be placed under mild sedation.  This depends on the behavior of the individual animal and mild sedation may be used to ensure the animal is both calm and safe (O’Brien, Robeck, 2010).  Rates of conception depend on several factors such as sperm quality, dosage, and the timing of AI in relation to estrus.  Rates of conceptiom will also vary by species.

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Chris Schuck

Breeding Assistance

Breeding assistance procedures such as AI allow foster the balance between safe breeding and the maintenance of genetic diversity.  Sperm can also be stored and transported to other facilities for breeding or may be applied to ongoing conservation efforts (O’Brien, Robeck, 2010).

This storage of genetic material greatly decreases the need to transport an animal for breeding; directly eliminating any undue stressors for the animal (O’Brien, Robeck, 2010).  Sperm can be collected from a trained zoological animal or even post-mortem during a necropsy and stored indefinitely (O’Brien & Robeck, 2010).  Much has been learned from observing reproduction in animals in human care.  In fact, researchers have learned more about reproduction of some zoological species in one year than they could in over ten years of research in the wild.  Further, these methods can translate to global conservation practices.

Reproduction management depends on the timing and seasonality of the animal’s reproductive cycle. Reproductive timing is signaled by endocrine changes that direct dose-dependent hormonal shifts in the animal (Mani et al. 1994; Hafez et al. 2000).  Hormones such as estrogen, progesterone, and testosterone orchestrate reproductive activity and have physiological effects on various tissues in the animal.  These hormones are measured through blood and urine tests, collected through trained husbandry practices.

Breeding Prevention

For animals with an intact reproductive system, contraceptives disrupt reproductive cycles by interfering with the cyclicity of hormone production.  This regulates the animal’s endocrine system so that it prevents the production and release of cells known as gametes.  Subsequently, this significantly decreases the chance of pregnancy, although the animal continues to mate naturally.  Similar to humans, many forms of contraception do not entirely eliminate the chance of pregnancy from occurring.

Various methods are used to reduce or inhibit breeding.  Physical separation practices are occasionally used, but it is not the most humane option.  Most animals in breeding programs have specific social needs.  Marine mammals are highly social and thrive in unrestrictive enclosures that promote socialization.  Due to this, the use of contraception is favored over separation.

Contraceptives may be used in breeding programs to maintain active populations and ensure diversity.  There are different ways to use contraceptives.  They can help to regulate the timing of estrus to prepare a female for mating in a breeding program.  Additionally, there are both reversible contraceptives (which are preferred) and there are permanent options.

 

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Chris Schuck

 

Reversible Contraception

Reversible contraceptives are drug-based regiments that greatly reduce the chance of pregnancy. These are generally considered effective and recommended for certain management conditions (Dierauf,L. & Gulland 2001).

There are limited reports on the use of contraceptives in marine mammals including effects of contraceptives on pregnancy and lactation.  In pinnipeds, progestin (commonly known in Depo-Provera) is often administered during the breeding season (American Zoo and Aquarium Association Contraceptive Advisory Group, 2004).  This contraceptive regulates a female’s endocrine system by suppressing gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and lutenizing hormone (LH), which prevents the release of an egg (Mani et al. 1994).  This suppression greatly reduces the chance of pregnancy.  Male pinnipeds can be injected with the synthetic hormone leuprolide acetate before and during the breeding season.  However, pinnipeds can have injection site reactions and should be monitored after the injection (Calle, 2005).

There are limited reports on the use of contraceptives in cetaceans.  A dosage of 5mg medroxyprogesterone acetate (a synthetic variant of a naturally occuring hormone) has been used successfully for over 15 years in bottlenose dolphins (Asa et al. 2005).  However, there is little known about the efficacy, side-effects, or long-term use of contraceptives in killer whales (Orcinus Orca).

Permanent Contraception

Methods of permanent contraception include both surgery and immunocontraceptives and should only be considered when implementing specific breeding plans for individual animals.  Reversible contraceptive methods are always the preferred option.  Surgeries increase the animal’s likelihood of stress and complications may arise from the surgery or anesthesia.  Surgery should only be performed when all other methods have failed.  Ovariohysterectomy and tubal ligation procedures are not often used in cetaceans and pinnipeds due to the associated risks and the higher chances for post-operative complications (Asa et al. 2005).

Male surgical procedures may be considered.  Although, castration is almost always the surgical choice for cetaceans as they have intra-abdominal testes.  Vasectomy procedures carry a higher risk in cetaceans than castration.  Further, cetaceans are difficult to anesthetize and sterilization techniques have not been perfected.  The risk of infection outweighs the benefits of the procedure (Calle 2005). Laparoscopic techniques are being developed and may be a future solution, as this technique may provide a great alternative to castration (Dover 2000).

Unlike surgical procedures, immunocontraceptives are a better solution for permanent contraception.   It is a promising trend in fertility management, but it cannot be reversed as oral contraceptives can (Brown et al. 1996).  Immunocontraceptives prime the immune system by producing antibodies against certain proteins so the animal’s immune system recognizes sperm and egg proteins as foreign.  The now-primed immune system produces antibodies which bind to the sperm or egg to signal the immune system to clear the ‘pathogen’, thus destroying the egg or sperm (Bagavant et al. 2002).  In pinnipeds, the Porcine zona pellucida vaccine (PZP) has been administered in contraceptive trials to determine its immunological response.  These studies determined that this method of immunocontraception was effective in a variety of pinnipeds.  However, there were possible adverse health consequences noted that occurred in California sea lions.  There have not been any published studies to date on the efficacy of immunocontraceptives in cetaceans.

 

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Chris Schuck

Problems with Contraception in Marine Mammals

Contraceptives are infrequently used to maintain marine mammal populations.  Most cases of contraceptive use stems from adjusting dosage from other mammal studies.  It would be safer to make the assumption that contraception in marine mammals should be considered an ongoing global trial.  Much of the data has been extrapolated from other mammalian studies such as humans, dogs, primates, and rodents (Munson et al. 2005).  There are still great risks and side effects associated with contraception use that require constant monitoring of animals in human care to minimize these effects.  These animals are monitored so closely in zoological settings, vets can respond and correct health issues before they are exacerbated and become life-threatening. It is possible that other metabolic processes may be affected, leading to side effects and complications.

Additional classes of contraceptives may prove to be beneficial.  However, there is little to no research to support their use in marine mammals.  For example, Gonadotropin-releasing hormone antagonists such as deslorelin or leuprolide acetate could be an effective alternative to progestin because they have little significant side effects.  These reversible contraceptives work to suppress the hypothalamic-pituitary-gonadal axis (HPA axis) that changes ovarian cyclicity and testicular function.  However, there are concerns that ovarian activity may not resume after contraceptive use ends (Penfold et al. 2002).  Additionally, it suppresses testosterone.  A loss or change in testosterone levels could result secondary sex characteristics in males.  In addition, the HPA axis has a very important job in endocrine signaling of other hormones that are needed for different pathways such as the fight-or-flight response.  An alteration in the HPA axis could lead to other unwanted physiological side effects.  Likewise, androgen-based contraceptives such as Mibolerone can block luteinizing hormone release, but is impractical for behavioral reasons, as it increases aggression (Munson et al. 2005).

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Chris Schuck

Importance of Breeding Programs

Approaches based on scientific findings are important in managing breeding effectively.  Animal rights studies use cherry-picked data and anthropomorphic connections to get their misguided information delivered to the public.  Their information invokes feeling whether or not there is any accuracy to their statements.  This approach is scientifically and fundamentally wrong.  Only decisions backed by science can be in the best interest of the animal.

Effective breeding programs provide benefits for animals in human care, research, and the conservation of wild animals.  For example, research on wild killer whales is limited due to observation limitations and the lack of ability to safely collect samples.  The study of these animals in human care provides an opportunity to observe them up close and on a daily basis.  This can provide insight to the social and physiological aspects of the animal’s life.  Additionally, research costs for zoological animals is significantly lower.  Research in animal reproduction has lead to the ability to increase genetic diversity by inserting new genes into small genetic pools.

The data acquired from these programs directly impacts conservation efforts.  Breeding programs have been successful in the past and will continue to be important.  These programs, coupled with habitat restoration and conservation initiatives, provide an opportunity for the re-population of areas where a species may have become lost or threatened.  There are many successful stories of an entire species making a comeback through successful breeding and release programs.  Without these programs, a number of terrestrial and marine species would have suffered extinction.  These breeding programs allow genetic diversity for a population to be maintained and act as nature’s insurance policy against extinction.

 

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Literature Cited

Asa C.S., & Porton, I. J. 2005. Wildlife contraception: issues, methods, and applications. JHU Press.

Bagavant H., Sharp C., Kurth B., & Tung K.S. 2002. Induction and immunohistology of autoimmune ovarian disease in cynomolgus macaques (Macaca fascicularis). The American journal of pathology 160(1): 141-149.

Brown R.G, Kimmins W.C., Mezei M., Parsons J., and Pohajdak B. 1996. Birth control for grey seals. Nature (Lond) 379: 30-31.

Calle, P.P. 2005. Contraception in pinnipeds and cetaceans. Wildlife Contraception. Johns Hopkins Univ. Press, Baltimore, Maryland, 168-176.

Dierauf,L. & Gulland F.M. (Eds.). 2001. CRC handbook of marine mammal medicine: health, disease, and rehabilitation. CRC press.

Hafez E.S.E., & Hafez B. 2000. Folliculogenesis, egg maturation, and ovulation. Reproduction in Farm Animals. Lippincott Williams and Wilkins. Pennsylvania, EEUU 68-81.

Mani S.K., Allen J.M., Clark J.H., Blaustein J.D., & O’Malley B.W. 1994. Convergent pathways for steroid hormone-and neurotransmitter-induced rat sexual behavior. Science 265(5176): 1246-1249.

Marsh H., & Kasuya, T. 1986. Evidence for reproductive senescence in female cetaceans. Reports of the International Whaling Commission 8: 57-74.

Munson L., Moresco A., & Calle P. P. 2005. Adverse effects of contraceptives. Wildlife contraception 66-82.

Neto M., Ova I., Henriques A., Filho C., Salbany A., Roque L., et al. 2008. Husbandry training for artificial insemination, performed under controlled behavior on a female bottlenose dolphin (Tursiops truncatus) at Zoomarine, Portugal [Abstract]. Proceedings of the International Marine

O’Brien J.K, & Robeck T.R. 2010. The value of ex situ Cetacean populatons in understanding reproductive physiology and developing assisted reproductive technology fo ex situ and in situ species management and conservation efforts. International Journal of Camparative Physiology 23: 227-248.

Penfold L.M., Ball R., Burden I., Joechle W., Citino S.B., Monfort S.L., and Wielebnowski N. 2002.Case studies in antelope aggression control using a GnRH agonist. Zoo Biology 21(5): 435-448

Robeck, T.R.,& O’Brien J.K. 2005. Development and Application of Assisted Reproductive Technologies in Cetaceans. In P. Dollinger (Ed.), World association of zoos and aquariums. Marine conservation issues number 7. (pp. 8–10). Switzerland: WAZA Liebefeld-Bern.

Skinner S.M., Prasad S.V., Ndolo T.M., & Dunbar B.S. 1996. Zona pellucida antigens: targets for contraceptive vaccines. American Journal of Reproductive Immunology 35(3): 163-174.




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