Responses of American toad tadpoles to predation cues: behavioural response thresholds, threat-sensitivity and acquired predation recognition

Behaviour ◽  
2006 ◽  
Vol 143 (7) ◽  
pp. 877-889 ◽  
Author(s):  
Reehan S. Mirza ◽  
Maud C.O. Ferrari ◽  
Joseph M. Kiesecker ◽  
Douglas P. Chivers
Keyword(s):  
Threshold Concentration ◽  
Alarm Cues ◽  
Bufo Americanus ◽  
American Toad ◽  
Chemical Alarm Cues ◽  
Selective Forces ◽  
Response Thresholds ◽  
Innate Predator Recognition ◽  
Toad Bufo ◽  
Predator Odour

AbstractPredation is one of the most important selective forces acting on prey animals. To respond adaptively to predation threats and increase their chances of survival, prey animals have to be able to recognize their potential predators. Even though a few studies demonstrated innate predator recognition, the vast majority of animals have to rely on learning to acquire this information. Often aquatic prey animals can learn to recognize predators when they detect conspecific alarm cues associated with cues from a novel predator. In this study, we exposed American toad (Bufo americanus) tadpoles to varying concentrations of chemical alarm cues (cues from injured conspecifics). We identified a concentration of cues which caused an overt antipredator response (supra-threshold concentration) and a lower concentration for which the prey failed to exhibit a response (sub-threshold concentration). In a second experiment, we attempted to condition the tadpoles to recognize the odour of larval dragonflies (Anax sp.) by pairing the dragonfly odour with either the sub-threshold concentration or the supra-threshold concentration of alarm cues. In both cases, the tadpoles learned to recognize the predator based on this single pairing of alarm cues and predator odour. Moreover, the intensity of the learned response was stronger for tadpoles conditioned with the supra-threshold concentration of alarm cues than the sub-threshold concentration. This is the first documented case of this mode of learning in anuran amphibians. Learned recognition of predators has important implications for survival.

scholarly journals Living in mixed species groups promotes predator learning in degraded habitats

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Douglas P. Chivers ◽  
Mark I. McCormick ◽  
Eric P. Fakan ◽  
Randall P. Barry ◽  
Maud C. O. Ferrari
Keyword(s):  
Predation Risk ◽  
Abiotic Factors ◽  
Alarm Cues ◽  
Learning Mechanisms ◽  
Trade Offs ◽  
Chemical Alarm Cues ◽  
Pomacentrus Amboinensis ◽  
Predator Foraging ◽  
Predator Learning ◽  
Predator Odour

AbstractLiving in mix-species aggregations provides animals with substantive anti-predator, foraging and locomotory advantages while simultaneously exposing them to costs, including increased competition and pathogen exposure. Given each species possess unique morphology, competitive ability, parasite vulnerability and predator defences, we can surmise that each species in mixed groups will experience a unique set of trade-offs. In addition to this unique balance, each species must also contend with anthropogenic changes, a relatively new, and rapidly increasing phenomenon, that adds further complexity to any system. This complex balance of biotic and abiotic factors is on full display in the exceptionally diverse, yet anthropogenically degraded, Great Barrier Reef of Australia. One such example within this intricate ecosystem is the inability of some damselfish to utilize their own chemical alarm cues within degraded habitats, leaving them exposed to increased predation risk. These cues, which are released when the skin is damaged, warn nearby individuals of increased predation risk and act as a crucial associative learning tool. Normally, a single exposure of alarm cues paired with an unknown predator odour facilitates learning of that new odour as dangerous. Here, we show that Ambon damselfish, Pomacentrus amboinensis, a species with impaired alarm responses in degraded habitats, failed to learn a novel predator odour as risky when associated with chemical alarm cues. However, in the same degraded habitats, the same species learned to recognize a novel predator as risky when the predator odour was paired with alarm cues of the closely related, and co-occurring, whitetail damselfish, Pomacentrus chrysurus. The importance of this learning opportunity was underscored in a survival experiment which demonstrated that fish in degraded habitats trained with heterospecific alarm cues, had higher survival than those we tried to train with conspecific alarm cues. From these data, we conclude that redundancy in learning mechanisms among prey guild members may lead to increased stability in rapidly changing environments.

Characterization of the spermiation response, luteinizing hormone release and sperm quality in the American toad (Bufo americanus) and the endangered Wyoming toad (Bufo baxteri)

2000 ◽  
Vol 12 (2) ◽  
pp. 51 ◽  
Author(s):  
Amy R. Obringer ◽  
Justine K. O'Brien ◽  
Robin L. Saunders ◽  
Kazutoshi Yamamoto ◽  
Sakae Kikuyama ◽  
...  
Keyword(s):  
Sperm Quality ◽  
Sampling Interval ◽  
Sperm Production ◽  
Bufo Americanus ◽  
American Toad ◽  
Non Invasive ◽  
Lh Release ◽  
Wyoming Toad ◽  
Toad Bufo

Spermiation and LH release in response to several methods of LHRH administration were assessed in the American toad (Bufo americanus), and the most successful method was tested in the endangered Wyoming toad (Bufo baxteri). Specific objectives were to: (1) compare spermiation responses and plasma LH concentration after invasive and non-invasive LHRH treatments; (2) evaluate sperm production in response to different LHRH dosages; (3) characterize the timing of sperm release post LHRH treatment; and (4) assess sperm quality (motility, viability, morphology and acrosomal status). Male American toads were administered 4 g LHRH by one of four routes: (1) intraperitoneal injection (IP); (2) subcutaneous injection (SQ); (3) dorsal dermis absorption (DDA); and (4) ventral dermis absorption (VDA). Aspermic urine only was collected from saline-treated controls and DDA animals. Several VDA animals released spermic urine; however, all LHRH-injected toads released spermatozoa. IP animals produced higher sperm and LH concentrations than SQ animals. The spermiation response in animals treated IP with 1 g LHRH was similar to that in animals treated with 4 g, but lower LHRH dosages tested produced inferior responses. Sperm production in responsive animals increased over time during the 12-h sampling interval. Regardless of treatment, most American toad spermatozoa were motile, viable, and acrosome-intact. Endangered Wyoming toads were treated IP with 4 g LHRH, and spermic urine was collected. Although most spermatozoa were viable and acrosome-intact, a considerable percentage possessed structurally abnormal heads. A single IP injection of LHRH appears to be a reliable and safe method for controlling spermiation in toads and may be useful for assisting endangered amphibian propagation.

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