Animal Ecology

The decline and disappearance of a range of giant marsupials, reptiles and birds from the Australian landscape during the last Glacial cycle continues to capture the imagination of both researchers and the general public. The events hinted at in the Australian fossil sequences appear to be mirrored on other continents through similar time periods, though the exact cause or sequence of extinctions remains largely unresolved. In recent years debate over megafaunal extinctions in Australia has been dominated by reports that humans were the primary drivers, leading some to assert that it is no longer a question of whether humans drove these extinctions, only how. Following the review of Wroe and Field, new reports have been published that claim support for a human-driven extinction (HDE). On closer scrutiny however, the key sites and samples lack firm contextual data and/or clear provenance. These studies fail to prove a key tenet of the HDE e that all, or even most now-extinct species were present at the time of human colonization of the continent. As compared with the easy assertion 5 years ago that this had been established, there are now more faunal species (c. 69% of total known to have become extinct) that cannot be placed within 50e100 ka of human arrival. There are still only two sites that demonstrate a coexistence of humans with some species of megafauna e Nombe Rockshelter in the PNG highlands and Cuddie Springs in the semi-arid southeast of Australia. If there is so little empirical evidence for coexistence or association of megafauna with humans, then support for an HDE through overhunting and ecosystem disruption is seriously compromised. Furthermore, the popularly cited "extinction window", proposed as c. 51e39 ka when the HDE is argued to occur, is still only a theoretical construct. There is no clear evidence indicating that this period was particularly significant in terms of faunal loss. At present, the great majority of 'Pleistocene' sites remain poorly dated and the understanding of faunal turnover through this epoch is almost non-existent. Small datasets, poorly constructed hypotheses and assertive rhetoric are the prominent features of current discussions on a human role in megafaunal extinctions. Importantly, it is yet to be established whether the extinctions are an archaeological problem. The sparse fossil record known from Australia hampers a clear resolution as to how and when the megafauna disappeared, a situation likely to continue into the near future.

The study of animal movement in wild, free ranging species is fundamental for advancing knowledge on ecosystem relationships and for conservation. The deployment of biologging devices to this purpose (often GPS-collars in large mammals) requires relatively invasive procedures, such as capture, handling and release. Capture and manipulation cause behavioural modifications that are largely understudied in wild species and may affect both the welfare of animals and the output of the studies. We evaluated post capture and release ranging behaviour responses of a small deer species (roe deer Capreolus capreolus) for five different capture methods across 14 study sites within the EURODEER collaborative project. Roe deer showed modifications in their movement behaviour, independently of the capture method. However, individuals recovered rapidly, converging towards the average behaviour within a relatively short interval of time (between 10 days and one month), demonstrating a general resilience to such stressful events. We encourage researchers to continually adapt capture and handling methods so as to minimize stress and prioritize animal welfare.

El monitoreo de poblaciones de caimán del Orinoco (Crocodylus intermedius) por medio de conteos nocturnos es esencial para evaluar tendencias, pero estos conteos muestran una gran variabilidad por factores que no siempre están bajo control en las investigaciones. El conteo de nidos o de grupos de crías recién nacidas ofrece una mejor estimación del número de adultos en la población y es más confiable para evaluar tendencias a largo plazo. Se llevaron a cabo conteos nocturnos de poblaciones de C. intermedius en los ríos Cojedes, Manapire y Capanaparo. En comparación con la situación en los otros ríos, en los sectores evaluados del Cojedes la especie mostró índices de abundancia relativa (IAR) altos, pero menores a los que se encontraban en los años 1996-1997. En los segmentos evaluados del Capanaparo también parece haber ocurrido un declive de la población. En el Manapire existen pocas evaluaciones previas, insuficientes para hacer comparaciones. La búsqueda de nidos y crías recién n...

The visual fields of vultures contain a small binocular region and large blind areas above, below and behind the head. Head positions typically adopted by foraging vultures suggest that these visual fields provide comprehensive visual coverage of the ground below, prohibit the eyes from imaging the sun and provide extensive visual coverage laterally. However, vultures will often be blind in the direction of travel. We conclude that by erecting structures such as wind turbines, which extend into open airspace, humans have provided a perceptual challenge that the vision of foraging vultures cannot overcome.

Estimating animal population size is a critical task
in both wildlife management and conservation biology. Precise and unbiased estimates are nonetheless mostly difficult to
obtain, as estimates based on abundance over unit area are
frequently inflated due to the Bedge effect^ bias. This may
lead to the implementation of inappropriate management and
conservation decisions. In an attempt to obtain an as accurate
and conservative as possible picture of Eurasian otter (Lutra
lutra) numbers, we combined radio tracking data from a subset of tracked individuals from an extensive project on otter
ecology performed in Southern Portugal with information
stemming from other data sources, including trapping, carcasses, direct observation of tagged and untagged individuals,
relatedness estimates among genotyped individuals, and a minor contribution from non-invasive genetic sampling. In
158 km of water network, which covers a sampling area of
161 km2 and corresponds to the minimum convex polygon
constructed around the locations of five radio-tracked females,
21 animals were estimated to exist. They included the five
radio-tracked, reproducing females and six adult males. Density estimates varied from one otter per 3.71–7.80 km of river
length (one adult otter per 7.09–14.36 km) to one otter per
7.67–7.93 km2 of range, depending on the method and scale
of analysis. Possible biases and implications of methods used
for estimating density of otters and other organisms living in
linear habitats are highlighted, providing recommendations on
the issue.

"Home range behaviour is a common pattern of space use, having fundamental consequences for ecological processes. However, a general mechanistic explanation is still lacking. Research is split into three separate areas of inquiry – movement models based on random walks, individual-based models based on optimal foraging theory, and a statistical modelling approach – which have developed without much productive contact. Here we review recent advances in modelling home range behaviour, focusing particularly on the problem of identifying mechanisms that lead to the emergence of stable home ranges from unbounded movement paths. We discuss the issue of spatiotemporal scale, which is rarely considered in modelling studies, as well as highlighting the need to consider more closely the dynamical nature of home ranges. Recent methodological and theoretical advances may soon lead to a unified approach, however, conceptually unifying our understanding of linkages among home range
behaviour and ecological or evolutionary processes."