Death-feigning behaviour in Iphisa elegans: the second reported case in the Family Gymnophthalmidae (Reptilia: Squamata) / Comportamento de tanatose em Iphisa elegans: o segundo caso na Família Gymnophthalmidae (Reptilia: Squamata)

Death-feigning behaviour occurs when the animal simulates a state of immobility. This behaviour is described for some lizard families, among them the family Gymnophthalmidae with only one record. Iphisa elegans is a diurnal and terrestrial Amazonian gymnophtalmid lizard. It has cryptic behavior and moves rapidly on the ground, hindering observations of its behavior. We report a case at the Comodoro Municipality, Mato Grosso State, Brazil. An adult male of I. elegans, when manipulated, turned its venter up and put itself in a death-feigning posture. This species is preyed upon by birds, snakes and other lizards¸ possibly behaving this way when the cryptic behaviour or escape attempt fails. More studies are necessary to evaluate the efficiency of this behaviour, as well as its frequency of occurrence, using individuals of both sexes. We also suggest to evaluate if the orange venter of males could have any antipredation advantage.

Fingir-se de morto é um comportamento no qual o animal simula um estado de imobilidade. Esse comportamento é descrito em algumas famílias de lagartos, dentre as quais, a família Gymnophthalmidae com apenas um registro. Iphisa elegans é um lagarto gymnoftalmídeo amazônico diurno e terrestre. Possui comportamento críptico e move-se rapidamente pelo solo, dificultando observações de seu comportamento. Reportamos um caso no município de Comodoro, Estado do Mato Grosso, Brasil: um macho adulto de I. elegans, quando manipulado, virou seu ventre para cima e fingiu-se de morto. Esta espécie é predada por pássaros, serpentes e outros lagartos, possivelmente portando-se dessa forma quando o comportamento críptico ou tentativa de fuga falham. São necessários mais estudos para observar a eficiência desse comportamento, assim como sua frequência de ocorrência, usando indivíduos de ambos os sexos. Também sugerimos que deve ser avaliado se a coloração alaranjada no ventre dos machos poderia fornecer alguma vantagem antipredação.

Biology and management of the masked chafer Cyclocephala distincta Burmeister (Melolonthidae, Dynastinae, Cyclocephalini)

Adults of Cyclocephala distincta are flower visitors of Neotropical palms (Arecaceae) and commonly found in the Atlantic Forest of Pernambuco, Brazil. Males and females were collected in the wild and subjected to captive rearing and breeding. The egg hatching rate, the life cycle, longevity of immatures and adults, and oviposition parameters in captivity were analyzed. The average duration of the life cycle of C. distincta was 108.2 days (n = 45). The egg stage lasted on average 10.9 days, and the egg-hatching rate was 73.9%. The immature stage lasted on average 93.4 days. The larvae stage exhibited negative phototaxis, and the size of their head capsules increased at a constant rate of 1.6 between instars, following Dyar's rule. The average duration of the first instar was 24.8 days (n = 88), whereas the second and third instars lasted for 17.2 (n = 76) and 40.4 (n = 74) days respectively, and survival rates were 21.6%, 86.4% and 97.4%. The pre-pupal stage was recorded, and pupal chambers were built before pupation. The average number of eggs laid per female was 15.5, the total reproductive period lasted for 3.3 days, and the total fertility was 81.2%. Adults that emerged in captivity exhibited an average longevity of 18.9 days. Adult C. distincta exhibited thanatosis behavior upon manipulation, a strategy observed for the first time in Cyclocephala.

Playing dead to stay alive: death-feigning in Liolaemus occipitalis (Squamata: Liolaemidae) / Simulando a morte para manter-se vivo: tanatose em Liolaemus occipitalis (Squamata: Liolaemidae)

Predation is the major selective force that drives the development of a series of defense mechanisms by the species. These mechanisms are efficient in that it limits the ability of predators to detect, recognize and subdue their prey. In lizards for example, the tail loss and locomotor escape are the most common defensive behavior reported on the literature. Additionally, in response to external stimuli, some lizards exhibit a peculiar defensive behavior: death-feigning or thanatosis. Here we describe the first record of death-feigning in a population of Liolaemus occipitalis in a coastal sand dune habitat in Southernmost Brazil. A total of 86 individuals were tested. During handling 75.6 percent of lizards feigned death. The duration of this behavior was longer when the observer remained closer to the lizards, suggesting the ability of L. occipitalis to evaluate the predation risk.

A pressão exercida pela predação é a principal força seletiva que direciona o estabelecimento de uma série de mecanismos de defesa por parte das espécies. Esses mecanismos são eficientes na medida em que limitam a capacidade dos predadores em detectar, reconhecer ou subjugar suas presas. Em lagartos, por exemplo, os comportamentos defensivos mais frequentemente citados na literatura são a autotomia caudal e a fuga. Além disso, em resposta a estímulos externos, alguns lagartos podem exibir um comportamento peculiar: fingem-se de mortos (tanatose). Neste estudo descrevemos o primeiro registro de tanatose em uma população de Liolaemus occipitalis em área de dunas costeiras no extremo Sul do Brasil. Um total de 86 indivíduos foram testados. Durante o manuseio, 75,6 por cento dos lagartos exibiram o comportamento de tanatose. A duração deste comportamento foi maior quando o observador permanecia a distâncias mais curtas dos lagartos, sugerindo uma capacidade de L. occipitalis em avaliar o risco de predação.