Headstarting Turtles –
Is it a valid strategy for wildlife rehabilitators?
By Harriet Forrester
(© 2005 Harriet Forrester)
Introduction
Headstarting is the hatching and rearing of turtles in captivity until they reach a size that will discourage predation. Headstarted turtles may be kept in captivity anywhere from several months to a few years before they are released. There are two purposes: to boost populations, and/or to establish new nesting sites (most often used with sea turtles). Although some have argued that headstarting turtles increases their chances for survival, others believe that headstarting is useless if it does not address other causes of species decline. In some cases, it may actually be harmful to turtles.
Headstarting directly interferes with the early life stage of the turtle, is tremendously complex, and has the potential for harm if done incorrectly. Wildlife rehabilitators should not undertake headstarting projects on their own. Headstarting, if used at all, should only be attempted as part of a controlled research study conducted within scientific parameters. Without careful study, research, controls and knowledge, headstarting can physiologically and psychologically harm hatchlings, and potentially endanger wild populations.
Emergency Overwintering is not the same as Headstarting
On occasion, situations arise whereby a hatchling or group of hatchlings must be overwintered. These are emergency situations that are usually encountered when a hatchling is ill or injured and requires extended care, is found in the wild at a time when weather conditions prevent an immediate return (i.e., an abnormally warm November day that brings the turtle out of hibernation), hatching too late in the year for a safe release, or a nest containing hibernating hatchlings is disturbed or destroyed. Overwintering does deprive the hatchling of a normal start in life. However, in these emergency situations, the turtle would not survive at all without assistance. This is not the same as deliberately keeping healthy turtles in captivity for the purpose of headstarting.
The Causes of Turtle Decline
The reason most often stated for headstarting turtles is protection from predators. However, turtles and their natural predators have been around for 200 million years. Natural predation is not causing turtle numbers to decline. Human-related activity is the number one cause of turtle population decline.
Pollution, habitat loss from overdevelopment, being hit by cars and lawn mowers, drowning in nets from shrimp, fishing, and crab operations, and collection for pets and food are the foremost problems faced by turtle populations today. These human-related threats affect all turtle and tortoise species in every part of the world (Moll and Moll 2000; Gibbons et al 2000; Gibbons et al 2001; McDougal 2000; Settle 1995; Garber and Burger 1995).
A major concern regarding headstarting is that it does not address these root causes of population decline (Pritchard 1980; Hewavisenthi and Kotagama 1990; Frazer 1992; Heppell et al 1996; National Research Council 1990). “Headstarting is useful only when used in tandem with a strategy that will reduce the loss of adults” (Klemens 1993).
Lessons from Sea Turtle Headstarting
The most completely documented headstarting programs have been done with sea turtles. After more than 30 years, the results are inconclusive at best. The serious problems encountered and the lack of proven successes have led to most of these programs being discouraged or discontinued (Sea Turtle Restoration Project 1995; Seigel 2000; Huff 1989; Great Barrier Reef Marine Park Authority 2005; Bryant 2002).
Detrimental effects of headstarting turtles
Wildlife rehabilitators care for sick, injured and orphaned wildlife in order to return a fully functioning animal to the wild. With this goal in mind, and based on the concerns raised by the sea turtle projects, many issues must be addressed regarding wildlife rehabilitators headstarting turtles.
1. Headstarting interferes with the natural life cycle of normal, healthy hatchlings. In the wild, turtles have no maternal care and are capable of finding food, water, hiding places, and hibernation spots the moment they emerge from the nest. Healthy hatchlings are, by definition, neither sick, injured, nor orphaned. There is no justification to disrupt this critical early life stage by keeping them in captivity under completely artificial circumstances. “Disrupting an animal's natural behavior and subjecting them to experiments without required controls or measurability is not scientifically legitimate management” (Woody 2001).
2. Incorrect artificial incubation can impact hatchlings and their survival ability. In many turtle species, the sex of the developing embryo is determined by the temperature at which the eggs are incubated. Temperatures off by only 2 or 3 degrees can skew sex ratios. Improper incubation conditions, including temperature, air flow, substrate material and humidity, can produce weak or deformed hatchlings, and even cause an entire clutch to fail to develop. Correct incubation temperatures, humidity, and substrate information can be found in the references listed under Recommended Reading, as well a number of other sources, and wildlife rehabilitators should consult these before attempting to artificially incubate turtle eggs.
3. Human interference and headstarting can have behavioral impact on hatchling turtles. Turtles that are consistently exposed to humans and human activity may become habituated and can lose their natural fear. Since humans are the number one predator of turtles, a fearless, habituated turtle will probably not survive long in the wild. For example, turtles in captivity rapidly learn that humans are the food source, and headstarted turtles may continue to associate the presence of humans with food (Pritchard 1980).
4. A hatchling’s development, both physiologically and psychologically, can be negatively impacted by captivity. According to J. B. Woody (1990) “…it doesn't take a genius to figure out that life in a bucket or raceway with a kind person dumping in prepared food pellets once a day is not what the real world is all about”. The following husbandry conditions have great influence on the proper physiological and psychological development of hatchlings:
Space: Headstarting is often done by rehabilitators using small containers, typically 2’ x l’ x l’, to raise hatchlings. Due to the limited space available for exercise, hatchlings will be lagging behind their wild counterparts in the muscle tone and stamina necessary to thrive in their natural environment. Tupperware or Rubbermaid containers with minimal or no furnishings are not suitable habitats. Captive environments must be enriched, which increases the well-being of the turtles by reducing stress, inducing exercise, and providing stimulation.
Crowding: Often, hatchlings are kept together in these small containers. In the wild, turtles do not congregate for any activity other than basking. Keeping a number of hatchlings together at all times in small spaces is abnormal and will increase stress, aggression, and food competition.
Water quality and levels: Even if water is filtered, it must still be changed frequently. This usually entails handling the hatchlings which gives rise to habituation concerns. The practice of keeping aquatic hatchlings in shallow water is an unnatural situation for them and limits the development of muscle tone and stamina.
Lighting: Incorrect levels of UV light can cause harm and behavioral disruption. UVB is needed to produce Vitamin D3, which is necessary to metabolize calcium. UVA stimulates normal behaviors such as basking and eating. Turtles can see into the ultraviolet range of light (Ammermuller 1998; Arnold 1987; Ventura 2001) and using the wrong lights can actually affect the way turtles visualize food items.
Photoperiod: Many reptiles obtain physiological cues from light/dark cycles. Inconsistent photo periods or constant light or dark environments induce stress. Light intensity and photoperiod can also affect hormone and neurotransmitter activity in chelonians, which in turn can impact food intake, stress levels, wound healing, and normal behavior (Vivien-Roels et al 1988; Kinsey et al 2003; Mahapatra et al 1988).
Temperature: As ectotherms, turtles depend on external sources to regulate their body temperature. The proper temperatures and temperature gradients are required for their metabolic processes to function. Temperature gradients are nearly impossible to achieve in the small containers typically used by rehabilitators.
5. Feeding behaviors and preferences are altered by captivity. Studies with turtles have shown that foods experienced early in life are preferred over those experienced later, and this can affect feeding choices. It has also been suggested that there is a food/olfactory “imprinting” in turtles (Burghardt 1977; Burghardt and Hess 1966). Unfortunately, it is difficult to duplicate a complex, natural, wild diet in captivity. Store-bought plants and domestic prey (such as mice) may differ from wild varieties in nutrient content, appearance, and taste (Donoghue 1996). If hatchling turtles are fed diets that look, smell and taste different from wild foods, they may become dependant on food that is not available to them after release.
6. Nutritional problems can be encountered in headstarting, including vitamin, mineral and protein deficiencies, overfeeding and obesity, and general malnutrition. There is no room for error in the diet of hatchlings. Most commercial diets are made from fish and crustacean meals. Mineral and vitamin contents of fish meals vary with species used, season of harvest, and processing techniques. Some processing techniques used in extrusion and pelleting commercial products involve high temperatures that partially destroy vitamins (Donoghue 1996).
Calcium deficiency, one of the most frequent and serious nutritional problems encountered in raising captive turtles, can result in metabolic bone disease. Both lack of calcium and excessive phosphorus are implicated in this problem. A good diet will have calcium/phosphorus (Ca/P) ratios of at least 2:1. Mealworms and crickets, which are items frequently used to feed hatchling turtles, have extremely poor Ca/P ratios of 1:10 or worse (Barker et al 1998; Finke 2002). High phosphorus levels may cause secondary hyperparathyroidism, bone resorption, and calcification of the kidneys and heart (Donoghue 1996).
7. Accelerated growth can harm hatchlings. Some headstart programs deliberately accelerate the growth of hatchlings to ensure that they are large upon release. Excessive growth rates in hatchlings have been associated with high mortality, renal disease, and irreversible deformities of the skeletal system (McArthur et al 2004).
8. Captive-reared turtles can introduce disease to wild
populations. A turtle can be a carrier of a pathogen (bacterial or viral
infections, or parasite loads), and still look and act perfectly healthy.
According to Dr. Elliot Jacobson, (1996), “Certain pathogens, and the diseases
they produce, are amplified in captivity, particularly in aquatic systems.
Releasing infected, asymptomatic turtles into unexposed wild populations can
result in disasters; that is, can result in major episodes of mortality”.
Releasing captive reared animals into the wild will always carry the risk of
inadvertent introduction of disease and parasites (Bell 2005).
Hatch and release – the alternative to headstarting
There are times when rehabilitators have to hatch turtle eggs. Gravid females may lay their eggs during rehabilitation, or eggs may be removed from a female that died. To ensure the best start in life for the resulting hatchlings, they should be released as soon after hatching as possible. If necessary, hatchling turtles can be kept for a few days to ensure absorption of the yolk sac. During that time, they live off the nutrients in the sacs, so there is no need to feed them. Immediate release introduces the hatchling turtle to its natural, wild habitat without any disruption from its natural life cycle. Turtles will not get habituated during this short time, and normal physical and behavioral development will take place in the wild.
Conclusions
Headstarting is not a proven technique. Short-term survival during the headstarting period and the appearance of health are not indicators that a truly healthy, fully-functioning turtle has been released to the wild. Turtles have been known to survive abysmal husbandry, horrific diets, injuries that would have killed another species, freezing, and even euthanasia attempts.
Research has shown that headstarting is not a valid recovery strategy; furthermore, it does not deal with the major causes of turtle decline – humans and their related activities. Comprehensive turtle recovery projects must simultaneously address all aspects of the problem: captive breeding, headstarting in some circumstances, predator control, habitat protection, public education, and long-term longitudinal studies. The research, planning, and expense required for such a project is beyond the resources of most rehabilitators. However, without that research, planning and follow-up, headstarting is just a guessing game. If the guesswork is wrong, the turtles are the ones that pay the price.
References:
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Recommended Reading
Ernst, C. H., J.E. Lovich, and R.W. Barbour. 1994. Turtles of the United States and Canada. Washington: Smithsonian Institution Press.
Highfield, A.C. 1996. Practical Encyclopedia of Keeping and Breeding Tortoises and Freshwater Turtles. London: Carapace Press.
Dodd, K.C., Jr. 2001. North American Box Turtles: A Natural History. Norman: University of Oklahoma Press.