Parks, people, and conservation: A review of management issues in nepal's protected areas

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43480/1/11111_2005_Article_BF01254607.pd

From Abbott Thayer to the present day: what have we learned about the function of countershading?

Of the many visual characteristics of animals, countershading (darker pigmentation on those surfaces exposed to the most lighting) is one of the most common, and paradoxically one of the least well understood. Countershading has been hypothesized to reduce the detectability of prey to visually hunting predators, and while the function of a countershaded colour pattern was proposed over 100 years ago, the field has progressed slowly; convincing evidence for the protective effects of countershading has only recently emerged. Several mechanisms have been invoked for the concealing function of countershading and are discussed in this review, but the actual mechanisms by which countershading functions to reduce attacks by predators lack firm empirical testing. While there is some subjective evidence that countershaded animals match the background on which they rest, no quantitative measure of background matching has been published for countershaded animals; I now present the first such results. Most studies also fail to consider plausible alternative explanations for the colour pattern, such as protection from UV or abrasion, and thermoregulation. This paper examines the evidence to support each of these possible explanations for countershading and discusses the need for future empirical work

Efeitos de Fatores Ambientais na Reprodução de Tartarugas Environmental factors effects in turtles reproduction

Para as espécies de tartaruga que apresentam a determinação sexual dependente da temperatura da incubação o local e o momento da desova, exercem influências que vão além da definição do sexo dos embriões. A influência do local da desova se estende a todo o desenvolvimento embrionário afetando o comportamento e o tamanho dos filhotes. O momento em que ocorre a desova trará conseqüências ao ambiente térmico dos ninhos à medida que a temperatura e a umidade variam ao longo do ano. A umidade será decisiva nas trocas hídricas e gasosas entre os ovos e o meio afetando a absorção do vitelo e o crescimento dos embriões. As cheias e os alagamentos são importantes fatores de perda de ninhos nas espécies de tartaruga de água doce. A desova no momento adequado possibilita uma incubação segura, sem a interferência de alagamentos dos ninhos e conseqüente morte dos embriões. A predação dos ninhos varia de acordo com o local da desova, o tipo e a abundância de predadores e a profundidade da câmara de ovos. A escolha de pontos de desova no interior da vegetação, onde a taxa de predação é geralmente menor, nem sempre é a estratégia mais frequentemente adotada pelas tartarugas, uma vez que esse procedimento pode levar a uma maior exposição das fêmeas aos predadores, à diminuição do sucesso da eclosão ou a alterações na razão sexual provocadas por diferenças na temperatura da incubação.<br>Turtle species in which the sex determination is dependent of incubation temperature, the nest site and the laying moment will affect more than embryo sex determination. The influence of the laying site extends all over the embryonic development, affecting hatching weight and size. The time of the egg-laying will bring consequences to the nest thermal environment, as the temperature and humidity change throughout the year. The humidity will be decisive in gaseous and hydric exchanges between eggs and the environment, affecting yolk absorption and embryo growth. Floods and inundation are important factors related to nest loss in freshwater turtle species. Egg laying at the appropriated time makes a safe incubation possible, without the interference of nest inundation and subsequent embryo death. The nest predation varies according to the egg-laying site, type and abundance of predator and nest depth. The choice of areas in the middle of vegetation, where the predation rate is generally smaller, is not always the most used strategy by turtles, since this procedure can decrease the hatching success or provoke changes in sex ratio