By Daniel Stanton
Importance of Breeding Program
Captive Breeding programs have been developed since the 1960’s to provide a way to maintain captive populations and a variable gene pool, without depleting wild populations. These programs allow for sustainability across zoos and aquariums and give hope to protecting species from becoming extinct. These programs are not cheap and often come under fire from activist groups. That is why it is important to highlight the benefits of the programs and raise awareness.
- Breeding Programs provide the opportunity to re-populate areas where species are threatened through successful breeding and release programs, but the success rate depends on habitat restoration and conservation efforts that mirror the goals of the breeding program.
- Captive breeding programs have helped to save a number of marine and terrestrial species from going extinct, acting as an ‘insurance policy’ against extinction.
- Captive breeding also ensures a public education program, allowing people to connect with animals that are threatened or endangered so that they can be inspired to have a greater appreciation for the world that we live in. The revenue gained from patrons is used to support the care of the animals, conduct scientific research, support rescue and rehabilitation, and support breeding and conservation programs.
- Captive animals are ambassadors for their species and help raise public awareness about their importance and the need to protect them in the wild. By allowing the public to observe these animals up close and connect with them. This generates public awareness where zoo and aquarium patrons want to do their part to make a difference and work towards saving a species from endangerment and subsequent extinction.
- Research on some populations, such as wild orca populations, is limited due to the cost and time it takes to complete a study, while observing animals in captivity on a daily basis can provide insights to many aspects of the animal’s life. The cost of the research is also reduced when conducted in an aquarium or zoological setting. For example, research in animal reproduction has lead to the ability to increase genetic diversity by inserting new genes into small genetic pools.
Reproduction management depends largely on timing and seasonality, if it applies to the animal’s reproduction pattern. Nearly all pinnipeds have a breeding season where seasonality becomes important for reproductive management strategies (Calle 2005; Munson et al. 2005). This is also true for some cetaceans, such as Belugas. Other cetaceans have cycles of estrous periods throughout the year (Calle 2005). Reproductive timing is signaled by species-specific endocrine changes that direct dose-dependent hormone shifts in the animal’s body (Mani et al. 1994; Hafez et al. 2000). Estrogen, progesterone, and testosterone orchestrate reproductive activities and have physiological effects on various tissues in the animal. For animals with an intact reproductive system, contraceptives provide a way to disrupt reproductive cycles by interacting with the endocrine system to interfere with the cyclicity of hormone production. Essentially contraceptives regulate the animals endocrine system so that it maintains a state that prevents the production and release of gametes, therefore preventing the chance of pregnancy occurring during mating.
Assisted Reproduction Technology
Breeding support measures are often used to monitor the safety of the animals and to support the genetic diversity of the collection. There are a few support tools that help increase genetic diversity or reduce the risk of two animals hurting one another during breeding. One of which is artificial insemination. This tool allows for the elimination of behavioral incompatibilities and can facilitate an increase in genetic diversity because sperm can be stored and transported to other facilities for breeding or even conservation efforts (O’Brien & Robeck, 2010). In addition, it eliminates the need to transport animals for breeding, which puts more stress on the animal than an assisted reproduction procedure (Robeck & O’Brien, 2005; O’Brien & Robeck, 2010). Assisted reproductive strategies can be a valuable conservation tool because spermatozoa can be collected from a trained captive animal or even post-mortem during a necropsy and stored indefinitely (O’Brien & Robeck, 2010). We have learned a lot from the use of reproductive technologies in a captive environment that can translate to conservation practices (O’Brien & Robeck, 2010).
Most animals in facilities are trained for daily husbandry behaviors such as presenting their fluke or flipper for blood draw. Assisted reproductive methods are no different. The animals are trained to remain calm and still during the procedure and then rewarded with a huge payload combination of one-on-one interactions with a trainer, the animal’s favorite toy, or the animal’s favorite treat. Once spermatozoa are collected from a male, they are artificially inseminated using an endoscopy procedure using catheters (Neto et al. 2008). During the procedure the females may be under mild sedation or no sedation at all depending on what is necessary to keep the animal calm and safe (O’Brien & Robeck, 2010). The procedure lasts only 20-30 minutes and veterinary staff monitors the animal during the entire procedure (Robeck et al. 2004).
Conception rates artificial insemination depend on sperm dose, sperm quality, the timing of the artificial insemination in relation to estrus cycle and ovulation, and quality of the oocyte, which can be dependent on the age of the female (Marsh & Kasuya, 1986; O’Brien & Robeck, 2010). The success rate in dolphins and killer whales is 50-75% (Robeck et al. 2004)
Breeding programs can be a valuable conservation tool because spermatozoa can be collected from a trained captive animal or even post-mortem during an necropsy and stored.
The ebb and flow of breeding programs relies on using various methods to support breeding or inhibit breeding. While separation practices may be an option, it is not the most humane choice. Marine mammals are highly social and need the interactions provided in unrestrictive enclosures. Because of this, the uses of contraceptive methods are favored over separation. There are two contraceptive categories – reversible and permanent. Reversible contraceptives are only effective while the animal is taking the contraceptive orally or by injection. The second category requires surgery or an immune based strategy discussed below.
Reversible Contraceptive Options
Reversible contraceptive that is often used in pinnipeds is progestin (Medroxyprogesterone acetate – aka Depo-Provera), which is administered during the breeding season (American Zoo and aquarium Association Contraceptive Advisory Group, 2004). This contraceptive maintains a female animal’s reproductive tract in a state of nurturing so that it greatly reduces the chance of pregnancy occurring. During this state, the endocrine system is regulated to prevent pregnancy. Some of the most important hormones regulated is the suppression of gonadotropin-releasing hormone GnRH), follicale-stimulating hormone, (FSH) and lutenizing hormone (LH), which prevents the release of an egg (Mani et al. 1994). While this contraceptive can be taken orally, but the dose and efficacy has not been determined (Asa et al. 2005). There are reversible contraceptives for male pinnipeds as well. Males can be injected with leuprolide acetate before and during the breeding season. 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, which includes effects of contraceptives on pregnancy and lactation. Successful contraception in cetaceans includes medroxyprogesterone acetate 5mg, which has been successfully used for over 15 years in bottlenose dolphins (Asa et al. 2005).
Contraceptives are generally considered effective and recommended for certain management conditions (Dierauf,L. & Gulland 2001).
Permanent Contraceptive Options
Permanent contraceptive management strategies have been developed, but are only recommended when using caution and planning out specific breeding plans for each animal. Immmunocontraeptive are a newer trend in permanent contraceptives. Immunocontraceptives prime the immune system to recognize sperm and egg proteins by producing antibodies to those proteins. If the immune system is primed, then antibodies will be produced, bind to proteins on the egg and sperm, and the immune system will clear them from the body because it recognizes these antibody-tagged proteins in the same way it recognizes a pathogen (Bagavant et al. 2002). The Procine zona pellucida vaccine (PZP) has been administered to pinnipeds in contraceptive trials to determine the immunological response of the vaccination. These studies determined that this immunocontraception was effective in a variety of pinnipeds, however there were possible adverse health consequences that occurred in captive California sea lions. Furthermore this contraceptive method is permanent and cannot be reversed as it can with oral contraceptives (Brown et al. 1996).
If permanent contraceptive practices are desired, then immunocontraceptive may be the better option. This is largely due to the fact that female surgical procedures such as ovariohysterectomy and tubal ligation are not often used in cetaceans and pinnipeds due to the associated risks and the higher chances for post-surgical complications. Not to mention the challenges that invasive procedures pose during the surgical procedure and anesthetist (Asa et al. 2005). Male surgical procedures can also be considered, however castration is commonly the surgical choice because cetaceans have intraabdominal testes and vasectomies are more risky than castration due to the fact that cetaceans are difficult to anesthetize and sterilization techniques have not been perfected (Calle 2005). The development of laparoscopic surgery techniques may be a future solution to this problem and if developed, this technique may provide a great alternative to castration (Dover 2000).
Problems with Contraceptives in Cetaceans and Pinnipeds
One of the biggest problems with cetacean and pinniped contraceptives is that most data have been extrapolated from other mammalian studies (aka humans, rodents, primates, and dogs). Because of this, there is a great risk of side effects from the use of contraceptives (Munson et al. 2005). It is more appropriate to think of contraceptives in captive and free-ranging animals as an ongoing global trial. Luckily for those that are in captivity, constant care and monitoring minimizes adverse effects because vets are able to respond and correct health issues before they may be exacerbated and escalate to a life-threatening saturation. Because contraceptives affect endocrine physiology, it is possible that other metabolic processes can be affected leading to side effects and complications from contraceptive use.
While progestin is effective in managing a female animal’s reproductive system to reduce the chances of pregnancy during mating, long term use of progestin is not recommended by the AZA because it result in many complications such as endometritis (Uterine infection), pyometra (accumulation of pus in the uterus), hydrometra (distended fluid-filled uterus), endometrial mineralization, and uterine lesions and infertility (Calle 2005; Munson et al. 2005). Additionally, long-term use can result in fatal complications such as as mammary gland carcinoma and endometrial hyperplasia–the beginning stage of endometrial cancer, and even diabetes.
There are other classes of contraceptives that may be promising, but again the re is little research to support the use in pinnipeds and cetaceans. Gonadotropin-releasing hormone antagonists such as deslorelin or leuprolide acetate could be an effective alternative to progestin, as it has little significant side effects. It works to suppress the hypothalamic-pituitary-gonadal axis that changes ovarian cyclicity and testicular function. However, there are concerns that ovarian activity may not resume after contraception withdraws (Penfold et al. 2002). Because it also suppresses testosterone, a loss or a change in secondary sex characteristics may be seen in males. Likewise, androgen-based contraceptives such as Mibolerone can block Leutinizing hormone release, but increases intraspecific aggression, making the use of this contraceptive impractical for behavioral reasons (Munson et al. 2005).
Although the use of immunocontraceptives may be a permanent solution and an alternative to invasive procedures like laproscopies and other surgical procedures, they also have their own set of side effects. Because the immune system needs to be primed and self proteins have a low immunogenecity, the antigens to sperm and egg proteins need to be made more immunogenic so that the animal’s immune system will recognize the antigen and not treat it as ‘self’ to mount an immune reaction. The adjuvant that the vaccine is delivered with could increase nonspecific inflammatory response (Skinner et al. 1996). Additionally there is not a lot of consistency between studies. Studies use different vaccination protocols, different adjuvants, and different antigens, and even measured the outcomes differently.. The variation in the method makes it difficult to see congruency in the studies to conclude the efficacy of this contraception method (Munson et al. 2005). The side effects are dependent on all of these factors; therefore the safety of immunocontraception cannot be accurately determined.
Breeding programs come under fire by activist groups that have little scientific support to back up their statements. Majority of the support that is used is animal welfare studies that used cherry-picked data and written with bias. This creates the streamlining of misguided and manipulated facts to the public via social media and other outlets that make a biologist jobs harder.
Here is the reality, we all want to complain about something and all have an opinion about how something should be corrected. I normally don’t share my opinion in an Awesome Research article but I feel that it is warranted before someone takes this article and uses it in a way that it is not intended due to the controversial nature of this piece.
I believe that the following statement needs to be said: The studies presented in this article were conducted by biologists that adhere to the peer-review process; Biologist that are working to do what is best for the animals in both the wild and captivity. This article is about the promise of using breeding management strategies to maintain current captive collections and promote conservation of species in the wild so that the genetic diversity can be maintained.
It is clear that humans are having a negative impact on the world and these strategies are being developed to protect animals and hopefully prevent their extinction. I think it is important to understand that conservation is the goal we should be working on and any tool that we can develop will help us reach that goal.
Daniel Stanton has a passion for animals and conservation. He holds a Master’s of Science Degree in Biology from Winthrop University where he did his thesis on the evolution of circadian clock genes in the lower Metazoa. He is a Sr. Biological Scientist at the University of Florida, and has experience in various areas of biology. Mr. Stanton has presented his research at many scientific meetings and worked on many scientific publications in collaboration with fellow researchers. He believes that one person can make a difference and create a wave of positive change.
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 Animal Trainers Association 36: 18.
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., Steinman K.J., Gearhart S., Reidarson T.R., McBain J. F., & Monfort S.L. 2004. Reproductive physiology and development of artificial insemination technology in killer whales (Orcinus orca). Biology of Reproduction 71: 650-660.
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.