GPS tracking reveals landfill closures induce higher foraging effort and habitat switching in gulls

Background Landfills are a major subsidy for some animals, with implications for their life history and demography. Gulls feed extensively on food from landfills and closures are expected to have ecological consequences, but how this influences movement ecology is virtually unknown. Methods We used GPS-tracking to quantify foraging behaviour and habitat choice of lesser black-backed gulls (Larus fuscus) breeding at two colonies before and after closure of two nearby landfills. Results Following closure, gulls from both colonies travelled further and for longer to forage. Gulls also changed habitat selection, although this differed by colony - birds from one colony shifted to agricultural habitats, while at the other, increased their use of urban areas. These behavioural responses had no effect on adult body condition but hint at potential direct effects of higher foraging costs and indirect impacts by shifting to new habitats. Conclusions Our results demonstrate how landfill availability influences gull foraging movements and habitat selection. We also emphasize the value of biologging to detect rapid behavioural responses in contrast to more conventional demographic approaches, which is especially important for animals that spend the majority of their lives away from direct observation.

Spring foraging movements of an urban population of grey-headed flying foxes (Pteropus poliocephalus)

Flying foxes provide ecologically and economically important ecosystem services but extensive clearing and modification of habitat and drought combined with the planting of commercial and non-commercial trees across various landscapes, has meant flying foxes in Australia are increasingly seeking foraging resources in new areas. In 2011, grey-headed flying foxes formed a camp in Adelaide, South Australia, outside their previously recorded range. We used global positioning system telemetry to study the movements and foraging behaviour of this species in Adelaide in spring (September to November) 2015. High-frequency location data were used to determine the foraging range and the most frequently visited foraging sites used by each bat which were ground-truthed to identify forage plants. A total of 7239 valid locations were collected over 170 nights from four collars. Despite being a highly mobile species, the mean core foraging range estimate was only 7.30 km2 (range 3.3–11.2 km2). Maximum foraging distance from the camp in the Botanic Park was 9.5 km but most foraging occurred within a 4-km radius. The most common foraging sites occurred within the residential area of Adelaide and included introduced forage plant species, Lemon-scented gum (Corymbia citriodora) and Port Jackson fig (Ficus rubiginosa). Other observed movement activities included dipping behaviour on inland and marine waters and travel across flight paths around Adelaide airport. Our findings suggest that urban habitats in Adelaide provide sufficient foraging resources for grey-headed flying foxes to use these areas exclusively, at least in spring. This creates substantial opportunities for bats to interact with humans and their infrastructure.

Feeding ecology of blue rock pigeon (Columba livia) in the three districts of Punjab, Pakistan

Present paper provides information on the feeding regimens of the two genders of the blue-rock pigeon (Columba livia Linn.) in the sampled habitats of the three districts viz. Rawalpindi, Faisalabad and Bahawalpur of the Punjab province, Pakistan. This feral pigeon, considered ubiquitous species, inhabits both the grasslands and clumped environments to establish their roosts and nests. The study explored about comparable feeding proportions from three major habitats of the pigeons which were captured with medium sized mist-nets. For Rawalpindi in the winter season, the Zea mays was one of the predominant food item (30.6%) for males, and other ranked major food contents were (26.7%, 22.4% and 20.2%), and fairly similar feeding proportions were also recorded for the females (50.4%, 33.3%, 36.4% and 23.9%) for Carthamus oxyacantha, Hordeum vulgare, Triticum aestivum and Zea mays respectively. Evidently, no significant deviations in the existing food crops for the three sites for the feral pigeon were detected, which strongly suggested that the, modes of feeding habits among the sustainable roosts and nests which were closely located to food crops, exerted negligible impacts during intermittent pigeon foraging movements in the diurnal conditions.

Foraging movements are density-independent among straw-coloured fruit bats

Intraspecific competition in large aggregations of animals should generate density-dependent effects on foraging patterns. To test how large differences in colony size affect foraging movements, we tracked seasonal movements of the African straw-coloured fruit bat ( Eidolon helvum ) from four colonies that range from 4000 up to 10 million animals. Contrary to initial predictions, we found that mean distance flown per night (9–99 km), number of nightly foraging sites (2–3) and foraging and commuting times were largely independent of colony size. Bats showed classic central-place foraging and typically returned to the same day roost each night. However, roost switching was evident among individuals in three of the four colonies especially towards the onset of migration. The relatively consistent foraging patterns across seasons and colonies indicate that these bats seek out roosts close to highly productive landscapes. Once foraging effort starts to increase due to local resource depletion they migrate to landscapes with seasonally increasing resources. This minimizes high intraspecific competition and may help to explain why long-distance migration, otherwise rare in bats, evolved in this highly gregarious species.

The drivers and functions of rock juggling in otters

Object play refers to the seemingly non-functional manipulation of inanimate items when in a relaxed state. In juveniles, object play may help develop skills to aid survival. However, why adults show object play remains poorly understood. We studied potential drivers and functions of the well-known object play behaviour of rock juggling in Asian small-clawed ( Aonyx cinereus ) and smooth-coated ( Lutrogale perspicillata ) otters. These are closely related species, but Asian small-clawed otters perform extractive foraging movements to exploit crabs and shellfish while smooth-coated otters forage on fish. We thus predicted that frequent rock jugglers might be better at solving extractive foraging puzzles in the first species, but not the latter. We also assessed whether species, age, sex and hunger correlated with rock juggling frequency. We found that juvenile and senior otters juggled more than adults. However, rock juggling frequency did not differ between species or sexes. Otters juggled more when ‘hungry’, but frequent jugglers did not solve food puzzles faster. Our results suggest that rock juggling may be a misdirected behaviour when hungry and may facilitate juveniles' motor development, but it appears unrelated to foraging skills. We suggest future studies to reveal the ontogeny, evolution and welfare implications of this object play behaviour.

First explorations: ontogeny of central place foraging directions in two tropical seabirds

A widespread hypothesis for the ontogeny of behavior and decision-making is the early-exploration-later-canalization hypothesis. It postulates that juveniles are more exploratory and adults more consistent in their behavior. In addition, it is often assumed that naïve juveniles could overcome the costs of individual experience building by copying more the decisions of others than adults (early-conformism-later-self-defining hypothesis). Here, we compare the central place foraging movements of adults and postfledging juveniles in their first flights around the colony before dispersal and migration in two sympatric species of tropical seabirds: red-footed boobies and great frigatebirds. Using GPS records of individual movements, we analyzed the foraging directions of seabirds from the colony across successive trips. Juveniles of both species showed significant within-individual consistency in foraging direction but at lower levels than adults. Juveniles leaving the colony within the same time window showed significant but low between-individual resemblance in foraging direction at levels similar to adults. In both species, homing efficiency was lower in juveniles than in adults. Juvenile foraging directions were initially influenced by wind conditions, particularly in low wing loading frigatebirds. Wind conditions progressively lost influence on juvenile foraging directions during their first weeks of flights. In contrast, within-individual consistency, between-individual resemblance, and homing efficiency did not show signs of progression in juveniles. Our results support the early-exploration-later-canalization hypothesis but not the early-conformism-later-self-defining hypothesis. Relaxed constraints on self-feeding efficiency could favor high variability in postfledging tropical seabirds. Our simple approach could be applied to further test these hypotheses by comparing strategies across a wide range of central place foragers.