Fotos / Sonidos

Qué

Esparvero Estriado (Accipiter striatus)

Observ.

silviomontani

Fecha

Agosto 13, 2022 09:08 AM -03

Fotos / Sonidos

Qué

Rana Mono de Vientre Pintado (Phyllomedusa sauvagii)

Fecha

Diciembre 8, 2010 03:58 PM -02

Fotos / Sonidos

Qué

Rana de Celdillas Guayanesa (Pipa arrabali)

Observ.

esteban_koch

Fecha

Mayo 2, 2022 08:43 PM -04

Fotos / Sonidos

Qué

Sapo Común (Rhinella arenarum)

Observ.

rdsage

Fecha

Septiembre 12, 1982 07:06 PM -03

Descripción

These three photos show two interesting aspects of R. arenarum populations in Mendoza Province.
Photos 1-3 show irregularly arranged, bright yellow spots on the back and sides of this animal. Jose Cei (1959) made observations on the number of animals that had these spots. He found that in Mendoza and adjacent San Jose Provinces, up to one-quarter (25%) of a local population may be spotted. In nearby provinces like San Luis and Cordoba, none, or singleton spotted animals were found. So, there is a geographic part to what exists in this wide-spread species. What is the meaning/importance of these bright spots? In some strains of laboratory mice, similar, irregular spotting is well understood as happening because of cells are mutated to lack pigment (melanin) while the early embryo is forming the layer of cells that will ultimately become the skin of the mouse. The mutant cells multiply and ultimately form patches of of white skin and hair. Presumably, something like this is happening here, with clones of yellow-pigmented cells appearing on different parts of what will become the dorsal skin during embryological development. Nothing more than Cei's report seems to have been published about the biology of this unusual coloration.
Photos 2 and 3 show the second unusual condition in these Mendoza-San Jose toads - a reflex that Cei called "hypnotic" and "spastic". When one of these toads is disturbed, it assumes this position, with its legs pulled in close to the body, the back curled over, and the eyes closed. The animals remain like this for many minutes. Cei found that the frequency of this behavior was much higher than yellow-spotting, reaching 60 percent in some of these same Mendoza/San Jose populations. It was absent in populations from other populations. The behavior is probably an adaptive, defense against attack by predators. Making the body as compact as possible, and secreting the noxious fluids from the large glands on the dorsal surface presumably keeps predators from attacking and hurting the animals. But again, I haven't found further experimental studies that would support, or not, this claim.
This common toad is full of interesting things for naturalists to study!

Vida Silvestre es una entidad asociada a la Organización Mundial de Conservación