Suchergebnisse

We report on a long-term population study (started in 1969) of three sympatric
rodent species in a tropical Queensland (Australia) rainforest. Populations
were censused annually using live-trapping and individual marking on two grids
in different habitat types. Two of the species,
Melomys cervinipes and
Uromys caudimaculatus, are 'old endemics'
and have slower life-histories than the third species,
Rattus fuscipes, which invaded Australia more recently.
The numbers of all three species fluctuated markedly over the study period.
Rattus numbers started low, peaked in the early 1980s,
and then crashed to zero by 1993. In contrast, Melomys
climbed gradually throughout the study period but crashed to zero by 1996.
Melomys numbers increased in drier years whereas
Uromys numbers decreased, but these results were
confounded by autocorrelation over time. When the effects of time (year of
study) were removed statistically, the correlations with rainfall disappeared,
but the number of Rattus remained negatively correlated
with the number of Melomys on one grid. We discuss the
possibility that numbers of these two species are determined by a combination
of climate and interspecific competition.

Context The wide-ranging movement of African elephants (Loxodonta africana) is largely driven by the spatio-temporal distribution of water and forage, and often leads to their travelling outside of formally protected areas. With an increase in drier periods predicted across Africa due to climate change, it is critically important to understand how elephants physiologically respond to alterations in the availability and distribution of resources. Aims We assessed variation in the adrenal activity of elephants living in Kenya's Tsavo East National Park between wet and dry seasons, as well as among individuals found in Tsavo East National Park and privately protected Rukinga Wildlife Sanctuary (part of the Kasigau REDD+ wildlife corridor) in the dry season, when the area experiences an influx of elephants in search of alternative resources. Methods We opportunistically collected fresh elephant faecal samples across the two seasons and locations for analysis of faecal glucocorticoid metabolite (fGCM, a proxy for stress) and nitrogen (Nf, an indirect measure of diet quality) concentrations. The Normalised Difference Vegetation Index (NDVI) was employed as an additional indicator of habitat quality. Key results In Tsavo East N.P. Nf and NDVI were both significantly lower during the dry season, indicating poorer habitat quality compared with the wet season. Although elephant fGCM concentrations tended to be higher in the dry season than the wet, the differences were not significant. There was no difference between elephant fGCMs measured in Tsavo East N.P. and Rukinga W.S. during the dry season, nor in habitat quality between the two locations. Conclusions Elephants living in Tsavo may be physiologically unaffected by (or adapt to) typical seasonal changes in habitat quality that could lead to nutritional stress; however, whether this is the case during extended periods of severe drought requires further investigation. Rukinga W.S. provides a safe haven of sufficient habitat quality for elephants searching for alternative resources during this period. Implications Extended dry periods are likely to become increasingly common in semiarid savannahs, and implications for wildlife must be closely monitored. Privately protected land outside formally protected areas plays an important role in conservation efforts, which should be considered when making land management plans.

Australia, New Zealand, New Guinea, Wallacea, and the islands of the Pacific Ocean collectively possess 42% of the world's parrot species, including half of all Critically Endangered species. We used comparative methods to review the factors related to extinction risk of 167 extant and 5 extinct parrot species from this region, subsequently referred to as 'Oceania'. We tested a range of ecological and socio-economic variables as predictors of extinction risk for parrots in the region while controlling for phylogeny. Parrot species were most likely to be threatened if they had small historical ranges, large bodies, or a high dependency on forest, or if they were endemic to a single country, or native to a country with high unemployment. Our analysis identifies invasive species as an especially severe threat to the parrots of Oceania. We present maps of parrot species' diversity and draw attention to regions of conservation concern. Our comparative analysis presents an important overview of the factors contributing to the decline of parrots in Oceania, and provides a strong basis for comparison with other parts of the world. ; This research was funded by the Australian Research Council, Loro Parque Fundación, the Australian Government National Environmental Science Programme via the Threatened Species Research Hub and the Department of Education and Training of the Australian Government via an Endeavour Postdoctoral Research Fellowship (ERF-PDR-6086-2017) to George Olah.