Home About us Contact
|
Home About us Contact | ||
|
|
||
Lion Population (lion + population)
Selected AbstractsImplications of closed ecosystem conservation management: the decline of Rothschild's giraffe (Giraffa camelopardalis rothschildi) in Lake Nakuru National Park, KenyaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Rick A. Brenneman Abstract Giraffe were historically free-ranging across most of sub-Saharan Africa but are now most often confined to national parks, conservation areas, or private ranches. Five viable populations of Rothschild's giraffe (Giraffa camelopardalis rothschildi) remain in protected areas in Kenya and Uganda. The viable population in Uganda is Murchison Falls National Park and the four populations in Kenya are Lake Nakuru National Park (LNNP), Ruma National Park, Giraffe Manor, and Mwea Natural Reserve. The Kenya Wildlife Service queried a rapid decline in LNNP giraffe numbers falling from 153 individuals (1995) to 62 individuals (2002) and the failure of that population to recruit young in those years. Significantly reduced browse options, inbreeding depression and preferential lion predation were considered as potential reasons for this trend. Population genetic parameter estimates derived from multilocus genotype analyses suggest that the LNNP population was in good genetic health with respect to the likelihood of inbreeding depression. The population decline coincided with the drought attributed to the 1994 El Niño. Possible dietary complications from highly concentrated tannin levels because of forced over consumption of the park's declining acacia trees may have compromised young giraffe, making them easy and opportunistic prey for the park's lion population. Résumé Dans le passé, des girafes évoluaient librement dans une grande partie de l'Afrique sub-saharienne, mais elles sont désormais confinées le plus souvent dans des parcs nationaux, des aires de conservation ou des ranches privés. Cinq populations viables de girafes de Rothschild (Giraffa camelopardalis rothschildi) subsistent dans des aires protégées au Kenya et en Ouganda. La population viable d'Ouganda est celle du Parc National des Murchison Falls, et les quatre populations du Kenya sont celles du Parc National du Lac Nakuru (LNNP), du Parc National de Ruma, du Giraffe Manor et de la Réserve Naturelle de Mwea. Le Kenya Wildlife Service s'est interrogé au sujet du déclin rapide du nombre de girafes au LNNP qui est passé de 153 individus en 1995 à 62 en 2002, et de l'échec de cette population pour recruter des jeunes ces années-là. Des possibilités alimentaires réduites, une dépression due à l'inbreeding, et une prédation préférentielle par les lions ont été envisagées comme raisons de cette tendance. Des estimations des paramètres génétiques de la population dérivées d'analyses de génotypes multilocus suggèrent que la population du LNNP est en bonne santé génétique en ce qui concerne la possibilité de dépression causée par l'inbreeding. Le déclin de la population a coïncidé avec la sécheresse attribuée à El Niño en 1994. Il est possible qu'elle ait souffert de complications alimentaires à cause de taux de tanins très concentrés, parce qu'elle a été forcée de consommer à l'excès les acacias du parc, qui sont en déclin, et que ces complications aient nui aux jeunes girafes et aient fait d'elles des proies faciles pour la population opportuniste des lions du parc. [source] Impact of changing diet regimes on Steller sea lion body conditionMARINE MAMMAL SCIENCE, Issue 2 2008Shannon Atkinson Abstract A leading theory for the cause of the decline of Steller sea lions is nutritional stress, which led to chronic high juvenile mortality and possibly episodic adult mortality. Nutritional stress may have resulted from either poor quality or low abundance of prey. The objective of this study was to determine whether we could predict shifts in body condition (i.e., body mass or body fat content) over different seasons associated with a change in diet (i.e., toward lower quality prey). Captive Steller sea lions (n= 3) were fed three different diet regimes, where Diet 1 approximated the diet in the Kodiak area in the 1970s prior to the documented decline in that area, Diet 2 approximated the species composition in the Kodiak area after the decline had begun, and Diet 3 approximated the diet in southeast Alaska where the Steller sea lion population has been increasing for over 25 yr. All the animals used in this study were still growing and gained mass regardless of diet. Body fat (%) varied between 13% and 28%, but was not consistently high or low for any diet regime or season. Mean intake (in kg) of Diet 2 was significantly greater for all sea lions during all seasons. All animals did, however, tend to gain less body mass on Diets 2 and 3, as well as during the breeding and postbreeding seasons. They also tended to gain more mass during the winter and on Diet 1, though these differences were not statistically significant. Thus, changing seasonal physiology of Steller sea lions appears to have more impact on body condition than quality of prey, provided sufficient quantity of prey is available. Steller sea lions are opportunistic predators and are evidently able to thrive on a variety of prey. Our results indicate that Steller sea lions are capable of compensating for prey of low quality. [source] Inbreeding and density-dependent population growth in a small, isolated lion populationANIMAL CONSERVATION, Issue 4 2010M. Trinkel Abstract In South Africa, more than 30 small, enclosed game reserves have reintroduced lions over the last two decades, which now house more than 500 individuals. There is a high risk of inbreeding in these fragmented, fenced and isolated populations, which may be compounded by a lack of management guidelines. A population of 11 founder lions Panthera leo was reintroduced to Madikwe Game Reserve in 1995, and this population has in turn become a source for reestablishing other populations. Only four lineages were reintroduced, founder males were related to founder females, and since 1997, only one male lineage maintained tenure for >9 years, resulting in breeding with direct relatives. Interventionist management to limit lion population growth and inbreeding in Madikwe has taken the form of translocating, trophy hunting and culling of mainly sub adult lions. Despite this management, inbreeding started 5 years after reintroduction. Reproductive performance and thus population growth in Madikwe were dependent on the overall lion population density. When lion density was low, females first gave birth at a significantly younger age and produced larger litters, resulting in a high population growth rate, which decreased significantly when lion density in the park reached carrying capacity, that is, 61 lions. This might have profound consequences for future reestablishment of lion populations when restocking new reserves: our study illustrates the need for founder populations of reintroduced endangered predator species to be as large and genetically diverse as possible, and thereafter new genetic material should be supplemented. The development of such management guidelines is becoming very important as large predator populations become increasingly fragmented and managed as metapopulations. [source] Bergmann's rule in larval ant lions: testing the starvation resistance hypothesisECOLOGICAL ENTOMOLOGY, Issue 6 2003Amy E. Arnett Abstract., 1.,Body size of the ant lion Myrmeleon immaculatus follows Bergmann's rule , an increase in body size towards higher latitudes. The hypothesis that ant lion body size is larger in the north as an adaptation for starvation resistance was tested. 2.,In a laboratory experiment testing starvation resistance, survivorship curves differed among 10 ant lion populations for both a starved and a fed treatment. 3.,The average number of months survived by each population was correlated positively with latitude for both treatments. Across both treatments and all populations, large individuals survived longer than small individuals; however individuals from high latitudes had higher survivorship, even after factoring out variation due to initial body size. 4.,These results suggest that starvation resistance may be an adaptation for coping with reduced prey availability in high latitudes. Starvation resistance may contribute to latitudinal gradients in body size of ant lions and other ectotherms. [source] Inbreeding and density-dependent population growth in a small, isolated lion populationANIMAL CONSERVATION, Issue 4 2010M. Trinkel Abstract In South Africa, more than 30 small, enclosed game reserves have reintroduced lions over the last two decades, which now house more than 500 individuals. There is a high risk of inbreeding in these fragmented, fenced and isolated populations, which may be compounded by a lack of management guidelines. A population of 11 founder lions Panthera leo was reintroduced to Madikwe Game Reserve in 1995, and this population has in turn become a source for reestablishing other populations. Only four lineages were reintroduced, founder males were related to founder females, and since 1997, only one male lineage maintained tenure for >9 years, resulting in breeding with direct relatives. Interventionist management to limit lion population growth and inbreeding in Madikwe has taken the form of translocating, trophy hunting and culling of mainly sub adult lions. Despite this management, inbreeding started 5 years after reintroduction. Reproductive performance and thus population growth in Madikwe were dependent on the overall lion population density. When lion density was low, females first gave birth at a significantly younger age and produced larger litters, resulting in a high population growth rate, which decreased significantly when lion density in the park reached carrying capacity, that is, 61 lions. This might have profound consequences for future reestablishment of lion populations when restocking new reserves: our study illustrates the need for founder populations of reintroduced endangered predator species to be as large and genetically diverse as possible, and thereafter new genetic material should be supplemented. The development of such management guidelines is becoming very important as large predator populations become increasingly fragmented and managed as metapopulations. [source] | ||||||||||