ABSTRACT

From 1978 to 2006, oviposition was induced in 13 North American turtle species. Of 245 inductions, 195 used oxytocin alone, 22 used arginine vasotocin (AVT) alone, 13 used a combination of oxytocin and ketamine, 8 combined propranolol and oxytocin, and 7 used propranolol and AVT. For wild Chrysemys picta picta, oxytocin-induced eggs were as viable as natural nest eggs. Suggested dosage ranges for oxytocin used alone vary from 0.7 to 4.0 units per 100 g, depending on species. In species where more than 28 animals were injected with the suggested dosage all eggs were oviposited after the first injection between 74% and 82% of the time. With a second injection, all eggs were laid between 83% and 94% of the time. It would be desirable to find a combination of easy-to-use drugs that yielded a higher success rate with the initial injection, especially for species with a history of not responding to oxytocin. Although only small numbers (13 animals) were involved, there was a suggestion that the combination of ketamine and oxytocin may prove more effective than oxytocin alone. A significant adverse effect observed with oxytocin induction was that some successfully induced turtles still displayed nesting behavior over the following days to weeks. This adverse effect might increase the risk of predation or trauma to wild animals after treatment with oxytocin. It might be avoided by using a more physiologic drug combination to induce oviposition rather than oxytocin alone. Natural oviposition is complex and, at least, involves the interaction of peripheral beta-adrenergic neurons, AVT, and prostaglandin F (PGF). Other, more physiologic approaches to induce oviposition might be to use a beta-adrenergic blocker with oxytocin or PGF, PGF +  oxytocin, PGF + ketamine, or oxytocin +  ketamine.

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