Data/hora: 10/06/2024 18:28:09

Biblioteca(s): | Embrapa Amazônia Oriental; Embrapa Pantanal.
Data corrente: | 14/03/1996
Data da última atualização: | 24/10/2014
Autoria: | MOREIRA, J. R.
Título: | The reproduction, demography and management of capybaras (Hydrochaeris hydrochaeris) on Marajo Island - Brazil.
Ano de publicação: | 1995
Fonte/Imprenta: | Oxford: University of Oxford, 1995.
Páginas: | 169 p.
Idioma: | Inglês
Notas: | Ph.D. Thesis.
Conteúdo: | The largest living rodent, the capybara (Hydrochaeris hydrochaeris) is found throughout Brazil. Considered to be one of the species with the most potential for sustainable harvest in South America, capybaras have actually been exploited since pre-Colombian times. Dues to its productive potential, importance to waterside people of the Amazon and the fact that its population is decreasing in certain areas of the region, the development of a capybara management system in the Brazilian Amazon is urgently needed. The purpose of this study is to evaluate the reproduction and demography of capybaras on Marajo Island (a site in the Brazilian Amazonia). The basic research methods used were census counts and hunting data. I also concentrate on aspects related to the sustainable harvesting of the capybara in South America, and discuss the present status of its conservation. Although capybara are seasonal breeders, males are fertile throughout the year. Capybara testes mass is closely associated with the production and activity of non-spermatogenic tissue (snout gland volum, anal gland volume and presence of coated hairs on the anal glands). There is a strong relationship between the scent glands and the volume of hormone producing tissue, and a negative relationship between the scent glands and the diameter of sperm producing tubules. The results of my analysis also suggest that dominance in capybaras is more associated to androgen-dependent scent glands than to sperm production. In accordance with what found for capybaras in Venezuela capybaras from Marajo Island breed throughout the year but have a peak in reproduction where most births occur (early rainy season). I estimate that the frequency of birth and fertility rate for capybaras in the seasonally flooded savannas of the Amazon and Orinoco basins are 1 birth/female/year and 2 females/female/year, respectively. Female capybaras from Marajo Island produce an average litter of 4.36 with 0.86 dead embryos. A total of 17.65% of the implanted embryos are lost in the course of gestation. The deaths of capybara embryos are not timed randomly throughout pregnancy. They occur at a particular period, probaly at an intermediate time of the gestation before the 60th day, and after a certain stage of developement most dead embryos are not resorbed, being kept to term. Apparently, male capybara embryos demand more nutrients than do their sisters, due to their higher rate of development. This affects the development and survivorship of adjacent embryos. I found that the position of the foetuses in relation to their sex in female capybara uteri is not random. These results also contradict those expected from the intrauterine position phenomenon, because instead of clustering foetuses of the same sex together a capybara foetus is usualy adjacent to one of the opposite sex. Moreover, larger litters are female biased while small litters are male biased. Farther, females in better condition have more dead foetus in their uteri, and these dead foetuses are more likely to be females. The average body weight of capybaras from Marajo Island is 47.50kg. The intrinsic rate of natural increase r max was high for capybaras, although being for mammalian populations inversely related to the body weight of the species. The age structure of the capybara population on Marajo Island indicated a rapid population turnover, with a high mortality rate within the first year. Therefore, life expectancy a birth for capybara on Marajo Island was very short. In a comparative analysis the family Hydrochaeridae was the family within the superfamily Cavioidea that usually had the heaviest individuals, the longest gestations, the oldest individuals to first reproduce, the largest, the heaviest young at birth, and the heavies litters. Within the Cavioidea superfamily no effect of the pattern of distribution was found on body weight, litter size, litter weight or relative litter weight. The relationship between body weight and the reproductive parameters for the superfamily Cavioidea followed the expected, with the exception opf that for litter size. Despite the negative correlation between body weight and litter size found when the data were not controlled for phylogeny, this relationships became positive when phylogeny was controlled for. The relationship between litter size and relative litter weight was negative. These was no significant relationship between body weight, litter size or relative litter weight and any of the ecological categories, when phylogeny was controlled for in the analyses. There was no difference between survivorship curves of hunted and unhunted populations. The model presented in this thesis has shown that the selective harvesting of capybara populations on the basis of sex may reduce fertility and lead the population to collapse. Although is supports a lower hunting mortality the removal of subadults and adults only provides a higher Maximum Sustained Yield than bunting all age-classes at random. Capybara numbers can be reduced for control reasons at a mortality rate 0.40 of the population, when all age-classes are removed at random. The model also predicts that the present capybara cropping regime from Venezuela may lead the population to extinction within 27 years and that the population could support the removal (of subadults and adults only) of only 0.17 of their individual. The productive potential of capybaras in the Neotropic calculated by the model (for a density of 100individuals/km2) was 841kg/km2/year. It is difficult to evaluate the general status of capybara populations but, although there may have been local extinctions, the capybara is not an endangered species. However, capybaras have been pushed well below carrying capacity by indiscriminate hunting. In Brazil, although there are some farms rearing capybaras in captivity, the economic viability of such farming is questionable in the face of stiff competition from pork, and the costs of eclosures, housing facilites and fodder. However, seasonally flooded savannas like those of the Pantanal Matogrossense and along the Amazon valley are suitable for capybara ranching in a similar manner to that practised in Venezuela. The harvesting scheme in use in Venezuela over the last 20 years mau have over-estimated the sustainable crop, but it nonetheless serves to demonstrate the capybara's productive potential and resistance to hunting pressure. However, the recdent reduction in capybara numbers in Venezuela indicates the need for a re-evaluation of the cropping limit, together with finer tuning of the hunting quotas and grat care in accurate population estimates.
Palavras-Chave: | Animal silvestre; Brasil; Capybara; Exploração sustentável; Ilha de Marajó; Management; Pará; Sustainable exploitation.
Thesagro: | Capivara; Demografia; Ecologia; Manejo; Reprodução; Zoologia.
Thesaurus Nal: | Amazonia; demography; ecology; Hydrochaeris hydrochaeris; Pantanal; reproduction; zoology.
Categoria do assunto: | --
Registro original: | Embrapa Amazônia Oriental (CPATU)

Exemplares:

CPATU - (31648-1) - ADD - TS - PP - 1995/005 - MOR - 1995/005 - DIS
CPAP - (31251-1) - ADD - TS - PP - TS96.00009 -  - 1996.00009 - DIS