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opencc-zeroSep 2020View details →

Data from: Temporal partitioning of activity: rising and falling top-predator abundance triggers community-wide shifts in diel activity

Top predators cause avoidance behaviours in competitors and prey, which can lead to niche partitioning and facilitate coexistence. We investigate changes in partitioning of the temporal niche in a mammalian community in response to both the rapid decline in abundance of a top predator and its rapid increase, produced by two concurrent natural experiments: 1) the severe decline of the Tasmanian devil due to a transmissible cancer, and 2) the introduction of Tasmanian devils to an island, with subsequent population increase. We focus on devils, two mesopredators, and three prey species, allowing us to examine niche partitioning in the context of intra- and inter-specific competition, and predator-prey interactions. The most consistent shift in temporal activity occurred in devils themselves, which were active earlier in the night at high densities, presumably because of heightened intraspecific competition. When devils were rare, their closest competitor, the spotted-tailed quoll, increased activity in the early part of the night, resulting in increased overlap with the devil's temporal niche and suggesting release from interference competition. The invasive feral cat, another mesopredator, did not shift its temporal activity in response to either decreasing or increasing devil densities. Shifts in temporal activity of the major prey species of devils were stronger in response to rising than to falling devil densities. We infer that the costs associated with not avoiding predators when their density is rising (i.e., death) are higher than the costs of continuing to adopt avoidance behaviours as predator densities fall (i.e., loss of foraging opportunity), so rising predator densities may trigger more rapid shifts. The rapid changes in devil abundance provide a unique framework to test how the non-lethal effects of top predators affect community-wide partitioning of temporal niches, revealing that this top-predator has an important but varied influence on the diel activity of other species.

opencc-zeroDec 2016View details →

Data from: A case for considering individual variation in diel activity patterns

There is a growing recognition of the role of individual variation in patterns emerging at higher levels of biological organization. Despite the importance of the temporal configuration of ecological processes and patterns, intraspecific individual variation in diel activity patterns is almost never accounted for in behavioral studies at the population level. We used individual-based monitoring data from 98 GPS-collared brown bears in Scandinavia to estimate diel activity patterns before the fall hunting season. We extracted 7 activity measures related to timing and regularity of activity from individual activity profiles. We then used multivariate analysis to test for the existence of distinct activity tactics and their environmental determinants, followed by generalized linear regression to estimate the extent of within-individual repeatability of activity tactics. We detected 4 distinct activity tactics, with a high degree of individual fidelity to a given tactic. Demographic factors, availability of key foraging habitat, and human disturbance were important determinants of activity tactics. Younger individuals and those with higher bear and road densities within their home range were more nocturnal and more likely to rest during the day. Good foraging habitat and increasing age led to more diurnal activity patterns and nocturnal resting periods. We did not find evidence of diel activity tactics influencing survival during the subsequent hunting season. We conclude that individual variation in activity deserves greater attention than it currently receives, as it may help account for individual heterogeneity in fitness and could facilitate within-population niche partitioning that can have population- or community-level consequences.

opencc-zeroDec 2015View details →

Data from: Density-dependent diel activity in stream-dwelling Arctic charr Salvelinus alpinus

Intraspecific competition plays a significant role in shaping how animals use and share habitats in space and time. However, the way individuals may modify their diel activity in response to increased competition has received limited attention. We used juvenile (age 1+) Arctic charr Salvelinus alpinus to test the prediction that individuals at high population density are more active and distribute their foraging activity over a greater portion of the 24-h cycle than individuals at low population density. Individually tagged fish were stocked in seminatural stream enclosures at low (2 fish/m2) and high (6 fish/m2) density. During each of two 2-week experimental rounds, activity of all fish within each enclosure was recorded every 3 h over seven 24-h cycles. At high density, fish were more active and distributed their activity over a greater portion of the 24-h cycle, with increased activity particularly at crepuscular times. Fluctuations in ecological conditions (e.g., water temperature and light intensity) also affected activity. Fish at high density grew as fast as fish at low density. This study demonstrates that individuals exhibit a degree of behavioral flexibility in their response to changes in ecological conditions and suggests that intraspecific competition can cause animals to modify temporal aspects of their activity to gain access to resources and maintain growth.

opencc-zeroDec 2017View details →

Data from: Non-uniform evolutionary response of gecko eye size to changes in diel activity patterns

Geckos feature a large range of eye sizes, but what drives this phenotypic diversity is currently unknown. Earlier studies point towards diel activity patterns (DAP) and locomotory mode, but phylogenetic comparative studies in support of the proposed adaptive mode of eye evolution are lacking. Here we test the hypothesis of DAP as the driver of eye size evolution with a dataset on 99 species of gecko. Results from phylogenetic generalized least square analysis (PGLS) and multivariate model-fitting reveal smaller eyes in diurnal geckos consistent with different phenotypic optima. However, Bayesian analyses of selective regime shifts demonstrate that only 2 of 9 transitions from nocturnal to diurnal activity are coupled with decreases in eye size, and 2 other regime shifts are not associated with DAP transitions. This non-uniform evolutionary response suggests that eye size is not the only functionally relevant variable. Evolutionary adaptations may therefore include different combinations of several traits (e.g., photoreceptors), all with the same functional outcome. Our results further demonstrate that DAP only partially explains eye size diversity in geckos. As open habitats favor the evolution of large eyes while obstructed habitats favor small eyes, the degree of habitat clutter emerges as another potential axis of eye diversification.

opencc-zeroNov 2019View details →

Data from: Fear of the dark? contrasting impacts of humans vs lynx on diel activity of roe deer across Europe

<ol> <li>Humans, as super predators, can have strong effects on wildlife behaviour, including profound modifications of diel activity patterns. Subsequent to the return of large carnivores to human-modified ecosystems, many prey species have adjusted their spatial behaviour to the contrasting landscapes of fear generated by both their natural predators and anthropogenic pressures. The effects of predation risk on temporal shifts in diel activity of prey, however, remain largely unexplored in human-dominated landscapes. </li> <li> We investigated the influence of the density of lynx (Lynx lynx), a nocturnal predator, on the diel activity patterns of their main prey, the roe deer (Capreolus capreolus), across a gradient of human disturbance and hunting at the European scale. </li> <li>Based on 11 million activity records from 431 individually GPS-monitored roe deer in 12 populations within the EURODEER network (http://eurodeer.org), we investigated how lynx predation risk in combination with both lethal and non-lethal human activities affected deer diurnality. </li> <li>We demonstrated marked plasticity in roe deer diel activity patterns in response to spatio-temporal variations in risk, mostly due to human activities. In particular, roe deer decreased their level of diurnality by a factor of 1.37 when the background level of general human disturbance was high. Hunting exacerbated this effect, as during the hunting season deer switched most of their activity to nighttime and, to a lesser extent, to dawn, although this pattern varied noticeably in relation to lynx density. Indeed, in the presence of lynx, their main natural predator, roe deer were relatively more diurnal. Overall, our results revealed a strong influence of human activities and the presence of lynx on diel shifts in roe deer activity. </li> <li>In the context of the recovery of large carnivores across Europe, we provide important insights about the effects of predators on the behavioural responses of their prey in human-dominated ecosystems. Modifications in the temporal partitioning of ungulate activity as a response to human activities may facilitate human-wildlife coexistence, but likely also have knock-on effects for predator-prey interactions, with cascading effects on ecosystem functioning. </li> </ol>

opencc-zeroMar 2022View details →

Mammals adjust diel activity across gradients of urbanization

Time is a fundamental component of ecological processes. How animal behavior changes over time has been explored through well-known ecological theories like niche partitioning and predator-prey dynamics. Yet, changes in animal behavior within the shorter 24-hour light-dark cycle have largely gone unstudied. Understanding if an animal can adjust their temporal activity to mitigate or adapt to environmental change has become a recent topic of discussion and is important for effective wildlife management and conservation. While spatial habitat is a fundamental consideration in wildlife management and conservation, temporal habitat is often ignored. We formulated a temporal resource selection model to quantify the diel behavior of eight mammal species across ten U.S. cities. We found high variability in diel activity patterns within and among species and species-specific correlations between diel activity and human population density, impervious land cover, available greenspace, vegetation cover, and mean daily temperature. We also found that some species may modulate temporal behaviors to manage both natural and anthropogenic risks. Our results highlight the complexity with which temporal activity patterns interact with local environmental characteristics, and suggest that urban mammals may use time along the 24-hour cycle to reduce risk, adapt, and therefore persist in human-dominated ecosystems.

Fig. 4 in Seasonal and Diel Activity of Dung Beetles (Coleoptera: Scarabaeoidea) Attracted to European Bison Dung in Białowieża Primeval Forest, Poland

Fig. 4. Faunistic resemblance of scarabaeoid dung beetle communities among six months of the vegetative season in Białowieża Primeval Forest, Poland.

Fig. 1 in Seasonal and Diel Activity of Dung Beetles (Coleoptera: Scarabaeoidea) Attracted to European Bison Dung in Białowieża Primeval Forest, Poland

Fig. 1. Study area in Białowieża Primeval Forest, Poland during the first collecting series on 14 April 2008. Photograph by A.Neumann.

Fig. 3 in Seasonal and Diel Activity of Dung Beetles (Coleoptera: Scarabaeoidea) Attracted to European Bison Dung in Białowieża Primeval Forest, Poland

Fig. 3. Seasonal dynamics and species richness of two scarabaeoid dung beetle nesting guilds in Białowieża Primeval Forest, Poland. Lines = number of individuals; bars = number of species.

Fig. 2 in Seasonal and Diel Activity of Dung Beetles (Coleoptera: Scarabaeoidea) Attracted to European Bison Dung in Białowieża Primeval Forest, Poland

Fig. 2. Structure of dung beetles communities in six months of the vegetative season in Białowieża Primeval Forest, Poland. Numbers above the charts indicate the number of individuals (number of species).

Fig. 6 in Seasonal and Diel Activity of Dung Beetles (Coleoptera: Scarabaeoidea) Attracted to European Bison Dung in Białowieża Primeval Forest, Poland

Fig. 6. Comparison of endocoprid and paracoprid guild abundance in material trapped during the day (6 am–6 pm) and at night (6 pm–6 am) in Białowieża Primeval Forest, Poland. * = p <0.05; ** = p <0.001.

Fig. 3 in Seasonal Appearance, Diel Flight Activity, and Geographic Distribution of MaleTelegeusis texensisFleenor and Taber (Coleoptera: Telegeusidae)

Fig. 3. Numbers of males (n = 99) at a single flight intercept per 10 minute intervals from 18:00–21:00, Stengl "Lost Pines" Biological Station, 2 May–27 June 2010.

Fig. 2 in Seasonal Appearance, Diel Flight Activity, and Geographic Distribution of MaleTelegeusis texensisFleenor and Taber (Coleoptera: Telegeusidae)

Fig. 2. Bar graphs of adult male Telegeusis texensis at Stengl "Lost Pines" Biological Station during the years of 2000–2002 and 2010. Gray bars represent abundance, diamonds represent daily maximum temperature, squares represent daily minimum temperature, and triangles represent daily precipitation.

Fig. 4 in Seasonal Appearance, Diel Flight Activity, and Geographic Distribution of MaleTelegeusis texensisFleenor and Taber (Coleoptera: Telegeusidae)

Fig. 4. Map of Texas counties with superimposed ecoregions and Telegeusis texensis collection localities plotted as black dots.

Fig. 1 in Seasonal Appearance, Diel Flight Activity, and Geographic Distribution of MaleTelegeusis texensisFleenor and Taber (Coleoptera: Telegeusidae)

Fig. 1. Cumulative bar graph of Telegeusis texensis abundance from 1990–2010 showing peak abundance and thus activity of adult males in April.