Sublethal predators and their injured prey: Linking aquatic predators and severe limb abnormalities in amphibians

Sunriver Nature Center, Box 3533, Sunriver, Oregon 97707, USA.
Ecology (Impact Factor: 4.66). 01/2010; 91(1):242-51. DOI: 10.1890/08-1687.1
Source: PubMed


While many predators completely consume their prey, others feed only on blood or tissue without killing the prey, sometimes causing ecologically significant levels of injury. We investigated the importance of sublethal predator attacks in driving an emerging issue of conservation importance: missing-limb deformities in amphibians. We combined long-term field data and manipulative experiments to evaluate the role of sublethal predation in causing abnormalities in two regions of central Oregon, U.S.A. Since 1988, western toads (Bufo boreas) in Lake Aspen have exhibited abnormalities dominated by partially missing limbs and digits at annual frequencies from <1% to 35%. On Broken Top volcano, we found comparable types and frequencies of abnormalities in Cascades frogs (Rana cascadae). Field sampling and observational data implicated two aquatic predators in these abnormality phenomena: introduced sticklebacks (Gasterosteus aculeatus) at Lake Aspen and corduliid dragonfly larvae (Somatochlora albicincta) at Broken Top. In experiments, these predators produced limb abnormalities identical to those observed in the respective regions. At Lake Aspen, in situ predator exclosures effectively eliminated abnormalities in toads, while comparisons among years with low and high stickleback abundance and between wetlands with and without sticklebacks reinforced the link between fish and amphibian abnormalities. Neither trematode parasite infection nor pesticide contamination could explain observed abnormalities. Our results suggest that predators are an important explanation for missing-limb abnormalities and highlight the ecological significance of sublethal predation in nature.

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Available from: Tracy Bowerman
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    • "There are numerous abiotic and biotic factors that may deteriorate the condition of animals and thus may shape the hostparasite interactions. Especially, sub-lethal effects of predators may greatly worsen the condition of the host (Vermeij, 1982; Bowerman et al., 2010). One of the best examples of this phenomenon is autotomy in some lizards species. "
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    • "014 ) also recorded very high occurrences of limb anomalies in laboratory colo - nies of A . mexicanum , especially when housed in high densi - ties . These resulted mainly from bite injuries that did not re - pair normally , and similar limb malformations can occur nat - urally in the absence of trematode infection ( Ballengée and Sessions 2009 ; Bowerman et al . 2010 ) . Thus , urodele limb malformations in extant populations have been known and studied for decades . However , such anomalies have not previously been recorded in a fossil sala - mander . Here , for the first time , we describe limb abnormali - ties in Jurassic salamander specimens from China ."
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    • "Several explanations are possible for the morphological anomalies found in the present study. Because the most frequent anomaly was the loss of hindlimbs, it is possible that anomalies were related to predator attack of juveniles and adults (Bowerman et al. 2010; Johnson and Bowerman 2010). Potential predators include birds (egrets, herons, storks, Kestrel, Falco tinnunculus, and Red-footed Falcon, Falco vespertinus), the European Pond Terrapin (Emys orbicularis), predatory fish, and aquatic arthropods (coleopterans, hemipterans, crayfish). "
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