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The battle over access to mates is perhaps one of the most extreme conflicts in evolution. Male to male conflict sometimes becomes so intense that it can result in the death of all males in a population. For example, in marsupials of the genera Antechinus and Dasyurus, the diseases that appear to follow from excessive investment in mating can wipe out all males in the population after the mating season. This is not harmful to population persistence, however, as inseminated females produce new males. If males can invest so much in sex that they eventually kill themselves, to what extent will they harm a potential mate?
The optimal hunting mortality rate and proportion of adult males in the harvest are found as functions of the size and structure of the saiga population before hunting. The effects of stochastic climatic variation on the population are taken into account in this model. It is shown that key assumptions must be made about the effects of the breeding sex ratio on female fecundity, and about whether poaching is occurring. If incorrect assumptions are made about either of these factors, the calculated optimal strategy can become severely suboptimal. A simple suboptimal decision rule that takes the population size and structure into account is shown to be more able to buffer against these factors…
Saiga tatarica is a member of the family Bovidae, and is native to Eurasia. It roams in herds from the lower reaches of the Volga River in Kazakhstan and Zungaria; and some are present in Mongolia. Because of near extinction due to hunting, the animal has been protected since 1920.
Retrospectively, antibodies titers $640 to T. gondii by indirect fluorescence were found in the sera of all three female and one male nilgais. No other cause of abortion was detected. Fatal toxoplasmosis was also diagnosed in one captive, adult female saiga antelope (Saiga tatarica), which died suddenly. Toxoplasma gondii was detected in the liver, lung, spleen, kidney, and intestine. An unusual finding was the presence of numerous tissue cysts in the liver of this animal. Toxoplasmosis was confirmed by PCR with TGR1E and immunohistochemically. Toxoplasmic hepatitis and pneumonia were considered to be the primary causes of death.
However, the greatest threat currently facing the Saiga is not the extinction in the early 1900s. The Saiga antelope has recovered only to find itself under serious threat once again. The political situation and habitat within the Saiga's range have changed substantially and demand for its horn in traditional Chinese medicine has led to uncontrollable poaching, leaving the long-term survival of the Saiga antelope far from certain.
Censuses are an important component of monitoring the status of
wildlife populations. Different techniques are used for different
species, on account of their specific biological characteristics.
The European population of the saiga antelope (Saiga tatarica)
inhabiting northwest Caspian Lowlands (eastern part of the Republic
of Kalmykia and south-western part of the Astrakhan Region) is in a
critical condition.
By the early 20th century, hunting had reduced Saiga Antelopes to near extinction but, following a ban on hunting, the populations recovered and commercial hunting of Saiga Antelopes resumed in the 1950s and continued until the late 1990s.
We test this hypothesis for the saiga antelope (Saiga tatarica),
a highly polygynous species with the highest level of maternal
allocation reported among ungulates. At such high reproductive
output levels, the limitations on additional investment in males
are likely to be particularly acute. However, we demonstrate high
levels of sexual dimorphism in both late-stage foetuses and newborn
calves, including within the same litter. Male twins with a brother
tended to be heavier than those with a sister. This may be due to
allocation constraints or differences in maternal quality. We
conclude that an explicit focus on potential constraints can
enhance the progress in the field of sex-specific…