Simone Ciuti

Applications of step-selection functions in ecology and conservation

Recent progress in positioning technology facilitates the collection of massive amounts of sequential spatial data on animals. This has led to new opportunities and challenges when investigating animal movement behaviour and habitat selection. Tools like Step Selection Functions (SSFs) are relatively new powerful models for studying resource selection by animals moving through the landscape. SSFs compare environmental attributes of observed steps (the linear segment between two consecutive observations of position) with alternative random steps taken from the same starting point. SSFs have been used to study habitat selection, human-wildlife interactions, movement corridors, and dispersal behaviours in animals. SSFs also have the potential to depict resource selection at multiple spatial and temporal scales. There are several aspects of SSFs where consensus has not yet been reached such as how to analyse the data, when to consider habitat covariates along linear paths between observations rather than at their endpoints, how many random steps should be considered to measure availability, and how to account for individual variation. In this review we aim to address all these issues, as well as to highlight weak features of this modelling approach that should be developed by further research. Finally, we suggest that SSFs could be integrated with state-space models to classify behavioural states when estimating SSFs.

Effects of Humans on Behaviour of Wildlife Exceed Those of Natural Predators in a Landscape of Fear

Background Human disturbance can influence wildlife behaviour, which can have implications for wildlife populations. For example, wildlife may be more vigilant near human disturbance, resulting in decreased forage intake and reduced reproductive success. We measured the effects of human activities compared to predator and other environmental factors on the behaviour of elk (Cervus elaphus Linnaeus 1758) in a human-dominated landscape in Alberta, Canada. Methodology/Principal Findings We collected year-round behavioural data of elk across a range of human disturbances. We estimated linear mixed models of elk behaviour and found that human factors (land-use type, traffic and distance from roads) and elk herd size accounted for more than 80% of variability in elk vigilance. Elk decreased their feeding time when closer to roads, and road traffic volumes of at least 1 vehicle every 2 hours induced elk to switch into a more vigilant behavioural mode with a subsequent loss in feeding time. Other environmental factors, thought crucial in shaping vigilance behaviour in elk (natural predators, reproductive status of females), were not important. The highest levels of vigilance were recorded on public lands where hunting and motorized recreational activities were cumulative compared to the national park during summer, which had the lowest levels of vigilance. Conclusions/Significance In a human-dominated landscape, effects of human disturbance on elk behaviour exceed those of habitat and natural predators. Humans trigger increased vigilance and decreased foraging in elk. However, it is not just the number of people but also the type of human activity that influences elk behaviour (e.g. hiking vs. hunting). Quantifying the actual fitness costs of human disturbance remains a challenge in field studies but should be a primary focus for future researches. Some species are much more likely to be disturbed by humans than by non-human predators: for these species, quantifying human disturbance may be the highest priority for conservation.

Human selection of elk behavioural traits in a landscape of fear

Among agents of selection that shape phenotypic traits in animals, humans can cause more rapid changes than many natural factors. Studies have focused on human selection of morphological traits, but little is known about human selection of behavioural traits. By monitoring elk (Cervus elaphus) with satellite telemetry, we tested whether individuals harvested by hunters adopted less favourable behaviours than elk that survived the hunting season. Among 45 2-year-old males, harvested elk showed bolder behaviour, including higher movement rate and increased use of open areas, compared with surviving elk that showed less conspicuous behaviour. Personality clearly drove this pattern, given that inter-individual differences in movement rate were present before the onset of the hunting season. Elk that were harvested further increased their movement rate when the probability of encountering hunters was high (close to roads, flatter terrain, during the weekend), while elk that survived decreased movements and showed avoidance of open areas. Among 77 females (2–19 y.o.), personality traits were less evident and likely confounded by learning because females decreased their movement rate with increasing age. As with males, hunters typically harvested females with bold behavioural traits. Among less-experienced elk (2–9 y.o.), females that moved faster were harvested, while elk that moved slower and avoided open areas survived. Interestingly, movement rate decreased as age increased in those females that survived, but not in those that were eventually harvested. The latter clearly showed lower plasticity and adaptability to the local environment. All females older than 9 y.o. moved more slowly, avoided open areas and survived. Selection on behavioural traits is an important but often-ignored consequence of human exploitation of wild animals. Human hunting could evoke exploitation-induced evolutionary change, which, in turn, might oppose adaptive responses to natural and sexual selection.

Red deer (Cervus elaphus) spatial use in the Italian Alps: home range patterns, seasonal migrations, and effects of snow and winter feeding

The spatial behaviour of 20 red deer was analyzed for the first time in the Italian Alps using radio-telemetry, from 1995 to 1997 in the Tarvisio forest, and from 1995 to 1999 in the Susa valley. Two distinct strategies of spatial behaviour were displayed in both study areas, i.e., migratory and stationary. Migratory red deer showed significantly larger annual home ranges, as each year they reached distant summer areas located at higher altitudes. Stationary red deer, instead, remained in the same areas throughout the year, with the exception of summer movement to neighbouring areas at higher altitude. As a consequence of these movements towards and from summer areas, spring and autumn migratory home ranges were significantly larger, while stationary home ranges recorded during spring, summer, and autumn were comparable in size. In winter home range sizes were limited in all monitored deer whenever snow cover reduced their mobility. Migratory red deer movements proved to be markedly affected by snowfall, with their monthly altitudes inversely correlated with snow presence on the ground. Stationary deer vertical movements proved less affected by presence of snow, as they reached lower altitude during summer. During winter, migratory red deer showed a greater use of the Tarvisio supplementary feeding stations, the only study site where this practice was in use. Migratory individuals probably adopted an opportunistic strategy, using the Alpine meadows at higher altitudes during the summer and the feeding stations during the winter, even if the use of feeding stations may be the end result of a poorer knowledge of trophic availability inside the winter areas. During the winter all the monitored deer used the same areas; food supply should be avoided in order not to promote high deer concentration and to reduce the risk of heavy forest browsing.

GPS based daily activity patterns in European red deer and North American elk (Cervus elaphus): indication for a weak circadian clock in ungulates.

Long-term tracking using global positioning systems (GPS) is widely used to study vertebrate movement ecology, including fine-scale habitat selection as well as large-scale migrations. These data have the potential to provide much more information about the behavior and ecology of wild vertebrates: here we explore the potential of using GPS datasets to assess timing of activity in a chronobiological context. We compared two different populations of deer (Cervus elaphus), one in the Netherlands (red deer), the other in Canada (elk). GPS tracking data were used to calculate the speed of the animals as a measure for activity to deduce unbiased daily activity rhythms over prolonged periods of time. Speed proved a valid measure for activity, this being validated by comparing GPS based activity data with head movements recorded by activity sensors, and the use of GPS locations was effective for generating long term chronobiological data. Deer showed crepuscular activity rhythms with activity peaks at sunrise (the Netherlands) or after sunrise (Canada) and at the end of civil twilight at dusk. The deer in Canada were mostly diurnal while the deer in the Netherlands were mostly nocturnal. On an annual scale, Canadian deer were more active during the summer months while deer in the Netherlands were more active during winter. We suggest that these differences were mainly driven by human disturbance (on a daily scale) and local weather (on an annual scale). In both populations, the crepuscular activity peaks in the morning and evening showed a stable timing relative to dawn and dusk twilight throughout the year, but marked periods of daily a-rhythmicity occurred in the individual records. We suggest that this might indicate that (changes in) light levels around twilight elicit a direct behavioral response while the contribution of an internal circadian timing mechanism might be weak or even absent.

LONG-TERM INFLUENCE OF HUMAN PRESENCE ON SPATIAL SEXUAL SEGREGATION IN FALLOW DEER (DAMA DAMA)

Abstract The present work investigates how a fallow deer (Dama dama) population in central Italy might have been affected from 1984 to 2003 by the increase of human access to the study site, where humans were the main deer predators. By using deer census data, possible correlations were analyzed between the increase in human presence and the response of each age and sex class. The numbers of different age and sex classes of deer recorded inside and outside the sector affected by human presence throughout the 20-year period of study were compared. A differential response was recorded among classes. Adult females and juveniles left this area (reducing their presence from 37% of all deer observed to 11% for adult females and from 19% to 3% for juveniles) when human pressure became higher, whereas the opposite result was true for males older than 24 months (adult males) that remained inside the disturbed sector (from 27% to 50% of deer observed). Intermediate values were recorded for yearling males, because they can be associated with both groups of females and groups of males. Results of this long-term study are best explained with the reproductive strategy hypothesis, because the increase of predation risk evoked a marked spatial sexual segregation in the fallow deer population. Females and juveniles used relatively predator-safe habitats, whereas males used habitats with higher predation risk but better food quality. Furthermore, as females increased their presence outside the disturbed sector, males gradually abandoned the undisturbed area, increased use of the disturbed sector, and maximized foraging opportunities by going to areas where indirect competition with females was probably reduced.

Space use, habitat selection and activity patterns of female Sardinian mouflon (Ovis orientalis musimon) during the lambing season

We analysed space use, habitat selection and activity patterns in female mouflons using radio tracking during lambing. During the birth period, mothers increased their home ranges to reach birth places suitably covered by Mediterranean scrubland. During lactation, mothers used Mediterranean scrubland more than non-mothers. Mothers decreased the use of meadows precisely when, according to a grass quality index, productivity of meadows was highest; this was likely due to the lack of concealment for lambs that would, thus, be vulnerable to eagle attacks. Accordingly, females are argued to adopt anti-predator tactics during lactation, trading high-quality foraging meadows for safer scrubland that provides good concealment for lambs. Despite the high temperatures recorded during the day in this period, lactating females showed greater activity levels, due to their need to meet greater energetic demands for lactation. This effort by mouflon mothers in such a poor environment as the Sardinian accounted for their lower productive success than in other European populations.

Ecological sexual segregation in fallow deer (Dama dama): a multispatial and multitemporal approach

We questioned the different interpretations of ecological sexual segregation from a novel perspective, i.e., by carrying out diverse temporal and spatial scale analyses within a long-term study (1984–2003). Thus we combined spatial (small/large) and temporal (small/large) scale analyses to identify the factors generating sexual segregation in fallow deer in San Rossore, Italy. The study site was divided into an eastern sector characterized by human disturbance (DS) and a western undisturbed sector (US). According to census data, human presence increased in DS from 1984, and while females gradually abandoned it, males remained—thus supporting the predation risk hypothesis (large spatial and temporal scale)—and actually increased their presence in DS, where they seemingly benefited from a lower female density. This supported the indirect competition hypothesis. The analysis of data on a large temporal and small spatial scale confirmed that intersexual competition, in particular for grass, was higher in a crowded pasture in US. Observations by means of radio-telemetry of 23 adult females and 25 adult males (1997–2001, reduced temporal and large spatial scale) showed that large scale segregation was relevant during the day and disappeared at night, when disturbance was absent and also the females reached DS. This also supported the predation risk hypothesis. Moreover, sexes showed different habitat choices inside DS at night, thus supporting the forage selection hypothesis (small spatial and temporal scale). In conclusion, failure to address the whole set of combinations of spatial and temporal scale analyses would have led to monocausal explanations of ecological sexual segregation.

Influence of sex, season, temperature and reproductive status on daily activity patterns in Sardinian mouflon ( Ovis orientalis musimon )

We analysed the influence of light/dark cycle, temperature, sex, season, and reproductive status on the daily activity patterns of 26 radiocollared mouflons (17 females, 9 males) in Sardinia. Data on their daily activity were collected from January 2006 to August 2007. Activity levels showed a 24-h bimodal pattern characterized by periodic cycles with increases and decreases peaking at dawn and dusk respectively. Beside being influenced by environmental temperatures, mouflons adjusted their daily activity seasonally and according to light/dark cycles. Only males significantly decreased their activity level in winter, i.e., when temperatures were lower, thus suggesting that males might be more sensitive to the cold winter weather than females. Males were generally less active than females presumably on account of the allometric relationship between body size and activity. However, as a consequence of the reproductive spur, males and females showed similar activity levels during the autumnal rutting season. In summer males and females without lamb significantly decreased their activity levels during the day, when the highest temperatures were recorded, while females with lamb did not. In fact, during the lambing season (late spring, summer) females with lamb persisted in being active during the day despite the increase of air temperature.

Dispersal Ecology Informs Design of Large-Scale Wildlife Corridors

Landscape connectivity describes how the movement of animals relates to landscape structure. The way in which movement among populations is affected by environmental conditions is important for predicting the effects of habitat fragmentation, and for defining conservation corridors. One approach has been to map resistance surfaces to characterize how environmental variables affect animal movement, and to use these surfaces to model connectivity. However, current connectivity modelling typically uses information on species location or habitat preference rather than movement, which unfortunately may not capture dispersal limitations. Here we emphasize the importance of implementing dispersal ecology into landscape connectivity, i.e., observing patterns of habitat selection by dispersers during different phases of new areas’ colonization to infer habitat connectivity. Disperser animals undertake a complex sequence of movements concatenated over time and strictly dependent on species ecology. Using satellite telemetry, we investigated the movement ecology of 54 young male elk Cervus elaphus, which commonly disperse, to design a corridor network across the Northern Rocky Mountains. Winter residency period is often followed by a spring-summer movement phase, when young elk migrate with mothers’ groups to summering areas, and by a further dispersal bout performed alone to a novel summer area. After another summer residency phase, dispersers usually undertake a final autumnal movement to reach novel wintering areas. We used resource selection functions to identify winter and summer habitats selected by elk during residency phases. We then extracted movements undertaken during spring to move from winter to summer areas, and during autumn to move from summer to winter areas, and modelled them using step selection functions. We built friction surfaces, merged the different movement phases, and eventually mapped least-cost corridors. We showed an application of this tool by creating a scenario with movement predicted as there were no roads, and mapping highways’ segments impeding elk connectivity.