Ecologia reprodutiva e comportamento de forrageio e escavação de Dermatonotus muelleri (Boettger, 1885) (Anura, Microhylidae)

Abstract

The majority of species which lives in environment with a high degree of temporal heterogeneity of the resources distributions presents specific adaptations which allow solving ecological problems. Dermatonotus muelleri is an endemic species which lives in a system of high impredictability, and presents specifics adaptations to the habitat. A population of D. muelleri was accompanied for two rainy seasons in Vitória Brasil, northwestern region of São Paulo State. The aims of this study were: determine the reproductive pattern of D. muelleri, with emphasis on the mechanisms which determine the synchronism between males and females, the regulation of the operational sex ratio (OSR), and the adaptability of D. muelleri to semi-arid environments by the forage and burrow behaviors. For determination of the OSR the abundance of males and females was estimated by visual encounter. The abundance of calling males was determined by survey at breeding site. These data were correlated with environmental factors (temperature, relative humidity and rainfall). Specimens collected were marked by toe clipping and the neighbor distance between calling males and between a clasped pair and a neighbor male were measured to verify the occurrence of sexual selection. The male and female behavior was observed by focal animal, all occurrence and ad libitum methods. The monthly abundance of males and females were positively correlated with the rainfall and with the minimum air temperature, and negatively with the air temperature variation. However, at a daily scale, was observed a time lag between the formation of the reproductive events and the environmental fluctuations, which could be associated with the termite reproductive fenology, the principal food item of D. muelleri. The males show no territoriality and exhibit two different patterns of active search behavior, which make improbably the occurrence of females sexual selection. Females rarely return in posterior reproductive events and stay in the pond a only night per reproductive event. The males mating call could be heard for great distances, and should stimulate females' reproductive behavior, but grants no opportunity for sexual selection by females. Males also exhibit behaviors which reduce costs to long distance communication (specific microhabitat selection to calling activity, reproduction in open areas, mating call emission with only one contraction of the chest region). The specialized feeding habits, the calling activity and the environmental fluctuations (rainfall, minimum air temperature and/or temperature air variation) are important to synchronous between males and females of D. muelleri during reproductive events. The foraging activity is modulated in accord to spatial distribution of the resources, being designed to an efficient harvesting of a key resource (Isoptera). These energy, harvested in a limited amount of time, must be sufficient to satisfied the reproduction and aestivation activities. In the other hand, the aestivation activity also contribute...

Environmental heterogeneity: Anuran diversity in homogeneous environments

“…Although the great majority of these species are generalists with broad areas of occurrence , some are explosive breeders (NOMURA 2005 and were found during short periods of the year. Species with this reproductive pattern may not be recorded when the samplings are made once a month.…”

Uso de fragmentos florestais por anuros (Amphibia) de área aberta na região noroeste do Estado de São Paulo

“…Várias espécies são encontradas enterradas durante a estação seca nessa região (D.C.Rossa-Feres, dados não publicados) e algumas, como Dermatonotus muelleri, entram em estivação permanecendo enterradas a mais de 50 cm de profundidade por até sete meses (Nomura 2003). Segundo Moreira & Barreto (1996), várias espécies como Scinax fuscovarius e Physalaemus cuvieri, registradas no presente estudo, já foram encontradas abrigadas dentro de cupinzeiros no cerrado durante este período.…”

Dimorfismo sexual, uso do ambiente e abundância sazonal de Elachistocleis cf. ovalis (Anura: Microhylidae) em um remanescente de Cerrado no estado de São Paulo, sudeste do Brasil

“…Alguns registros indicam que E. ovalis permanece a maior parte do ano enterrado, só saindo após chuvas fortes para se reproduzir (Barrio-Amorós 2004, Eterovick & Sazima 2004, outra estratégia comum para o grupo no bioma (Colli et al 2002). Estes dois comportamentos já foram observados em outro microhilídeo neotropical que ocorre no Cerrado, Dermatonotus muelleri (Nomura 2003).…”

“…De fato, o aumento de temperatura parece afetar o número de espécies em atividade reprodutiva em locais com sazonalidade climática acentuada (Vasconcelos & Rossa-Feres 2005, Prado et al 2005. Dentre os microhylideos, Dermatonotus muelleri teve abundância mensal positivamente correlacionada com a chuva e temperatura mínima do ar (Nomura 2003), enquanto que duas outras espécies australianas tiveram o número de machos vocalizantes ao longo do dia influenciado pela umidade relativa do ar (Hauselberger & Alford 2005). Possivelmente, outras variáveis não tomadas influenciam a atividade sazonal (e provavelmente diária) de E. cf.…”