Abstract
espanolLa cria en cautividad de especies amenazadas es un practica importante en la conservacion, pero no esta claro si los programas de cria en cautividad a largo plazo pueden afectar a determinados atributos fundamentales de la eficacia biologica de las especies como la capacidad de depredacion. En el presente estudio se estudian experimentalmente los efectos de la capacidad de depredacion de tritones del Kurdistan adultos nacidos en cautividad (CBN) y de individuos obtenidos directamente de la naturaleza (FLN) en la supervivencia y el crecimiento de renacuajos de sapo verde mantenidos en cuatro tratamientos de densidad de depredadores, que contenian cero, uno, dos y tres tritones. El grupo de tritones FLN mostro una tasa de depredacion rapida dependiente de la densidad de depredadores que conllevo que las tasas de supervivencia de los renacuajos en las densidades de control, baja, media y alta fueran, respectivamente, del 81%, el 74%, el 60% y el 17%. El grupo CBN tuvo una menor tasa media de depredacion sobre los renacuajos de B. variabilis, cuya tasa de supervivencia disminuyo hasta el 83%, el 81%, el 82% y el 77% para los tratamientos con cero, uno, dos y tres tritones, respectivamente. Sin embargo, a diferencia del grupo FLN, esta tasa de depredacion aumento significativamente con el tiempo y paso de 0,37 a 0,60 renacuajos por dia. Por otra parte, la tasa de crecimiento de los renacuajos criados con depredadores del grupo FLN fue significativamente superior a la de los renacuajos criados en contenedores de control sin depredadores. Como conclusion, nuestros resultados sugieren que la exposicion de individuos nacidos en cautividad del triton del Kurdistan a sus presas potenciales enriquece el medio ambiente y puede ser util para elaborar programas mas eficientes de cria en cautividad y reintroduccion de esta especie de anfibio muy amenazada. EnglishCaptive breeding of endangered species is an important conservation tool, but it is not clear how long–term captive breeding can influence fitness attributes such as predatory ability. We experimentally investigated the predatory impact of adult captive–bred newts (CBN) and adult free–living newts (FLN) on the survival and growth of larval green toad (B. variabilis) in four predator density treatments containing none, one, two, or three newts. FLNs performed a rapid density–dependent predation, yielding average survival rates of tadpoles in no, low, medium, and high densities to 81%, 74%, 60% and 17%, respectively. CBNs had an average lower predation rate on B. variabilis tadpoles with a decrease in survival rate of tadpoles to 83%, 81%, 82% and 77% for 0, 1, 2 and 3 predator treatments, respectively. However, contrary to FLNs, they exhibited a significant increase in predation rate with time from 0.37 to 0.60 tadpoles per day. In addition, the growth rate of tadpoles reared with predators for the FLN group was significantly higher than the growth rate of tadpoles reared in control containers without the predator. In conclusion, our findings suggest that exposing captive–born adult yellow spotted mountain newts to their potential prey enriches the environment, and may be a useful approach in the development of more efficient captive breeding and reintroduction programs for this highly endangered amphibian.
Highlights
Captive breeding programmes have been used for a number of endangered species to save them from extinction, but the long–term outcome of these programmes has not always been satisfactory for a variety of reasons (Hedrick and Fredrickson, 2008)
In all densities of newts, the predation rates on tadpoles were higher in free–living newts (FLN) than in captive–bred newts (CBN)
FLN predation rate was maximal (18.11 ± 13.91 eaten tadpoles) in the first interval but did not increase later, whereas the predatory ability of CBNs was low at the beginning but increased over time (3.66 ± 2.50 eaten tadpoles in the first interval to 7.33 ± 4.30 eaten tadpoles in the third interval)
Summary
Captive breeding programmes have been used for a number of endangered species to save them from extinction, but the long–term outcome of these programmes has not always been satisfactory for a variety of reasons (Hedrick and Fredrickson, 2008). The above–mentioned studies cast doubts on the value of captive breeding and subsequent reintroduction as a conservation tool for threatened amphibian species (Griffiths and Pavajeau, 2008), there are always situations in which the captive breeding is the only conservation option available (Stuart et al, 2004). Harding et al (2016) reviewed captive breeding programmes involving 213 amphibian species and found captive breeding affected various characteristics that could be taken into account in efforts to improve captivity management. Questions regarding the importance of captive breeding and subsequent reintroduction of threatened species will continue to appear as more studies are carried out on these programmes (Armstrong and Seddon, 2008), and, especially in view of the practical irreversibility of many current threats to amphibians in their natural environments, which makes captive breeding and reintroduction indispensable conservation methods (Griffiths and Pavajeau, 2008; Harding et al, 2016)
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