117 research outputs found
Code accompanying "Tracking snowmelt to jump the green wave: Phenological drivers of migration in a northern ungulate"
No full textThis is code and data related to "Tracking snowmelt to jump the green wave: Phenological drivers of migration in a northern ungulate" by Michel P. Laforge, Maegwin Bonar, and Eric Vander Wal
TrackingSnowmelt: Code for "Tracking snowmelt to jump the green wave: Phenological drivers of migration in a northern ungulate"
No full textThis repository contains code for "Tracking snowmelt to jump the green wave: Phenological drivers of migration in a northern ungulate" in Ecology. Authors: Michel P. Laforge, Maegwin Bonar, and Eric Vander Wal
Multiple density-dependent processes shape the dynamics of a spatially structured amphibian population
No full textUnderstanding the mechanisms that regulate the dynamics of spatially structured populations (SSP) is a critical challenge for ecologists and conservation managers. Internal population processes such as births and deaths occur at a local level, while external processes such as dispersal take place at an inter‐population level. At both levels, density dependence is expected to play a critical role. At a patch scale, demographic traits (e.g., survival, breeding success) and the population growth rate can be influenced by density either negatively (e.g., competition effect) or positively (e.g., Allee effects). At the scale of an SSP, although positive density‐dependent dispersal has been widely reported, an increasing number of studies have highlighted negative density‐dependent dispersal.
While many studies have investigated the effects of density on population growth or on dispersal, few have simultaneously examined density‐dependent effects at the scale of both the local population and the entire SSP. In this study, we examine how density is related to demographic processes at both the pond level (survival and population growth) and the SSP level (between‐pond dispersal) in a pond‐breeding amphibian, the great crested newt (Triturus cristatus). The study was based on 20 years of individual capture–recapture (CR) data (from 1996 to 2015) gathered from an SSP made up of 12 experimental ponds (“patches”).
We first used a CR multievent model to estimate both survival and dispersal rates in specific ponds as a function of distance between ponds. Then, using a second CR multievent model, we examined whether survival and recapture rates were influenced by population density in a pond. Lastly, we used state‐space time series models to investigate whether density affected population growth in each pond.
Our results found a positive density‐dependent effect on survival and a negative density‐dependent effect on departure. In addition, the findings indicate that population growth was negatively related to density in all 12 ponds.These results support the hypothesis that in SSPs, density may have multiple and contrasting effects on demographic parameters and growth rates within local populations as well as on dispersal. This study underlines the need to better understand how density dependence may influence potential trade‐offs between life‐history strategies and life‐history stages
Fear of the dark? Contrasting impacts of humans versus lynx on diel activity of roe deer across Europe
No full textHumans, 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.
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.
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 the diurnality of deer.
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 night‐time 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.
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
Data and code for Laforge et al "Consistent individual differences and plasticity in migration behaviour of three North American ungulates"
No full text<p>Data and code for the manuscript "<span>Consistent individual differences and plasticity in migration behaviour of three North American ungulates" by </span><span>Michel P. Laforge, Eric Vander Wal, Quinn M. R. Webber, Chris Geremia, Matthew J. Kauffman, Douglas E. McWhirter, Arthur Middleton, Tony W. Mong, Kevin L. Monteith, Anna C. Ortega, Hall Sawyer, and Jerod A. Merkle.</span></p>
Invited Commentaries on Shizuka & Johnson 2020, & Response from the Authors
No full textAdriana A. Maldonado-Chaparro and Damien R. Farine, Demographic processes in animal networks are a question of time
Amiyaal Ilany, Complex societies, simple processes
Orr Spiegel and Noa Pinter-Wollman, Placing the effects of demography on networks in ecological context
Ipek G. Kulahci, Individual differences can affect how networks respond to demography
Eric Vander Wal and Quinn M.R. Webber, Density dependence and eco-evolutionary dynamics of animal social networks
Daniel I. Rubenstein, On assessing the importance of demographic change for social structure
Daizaburo Shizuka and Allison E. Johnson, The long view on demographic effects on social networks: A response to comments on Shizuka and Johnso
<i>What Should a Clever Moose Eat?: Natural History, Ecology, and the North Woods</i>. By John Pastor; illustrated by the author. Washington (DC): Island Press. $30.00 (paper). xxxvi + 298 p.; ill.; index. ISBN: 978-1-61091-677-6. 2016.
No full textSex, friends, and disease: social ecology of elk (Cervus elaphus) with implications for pathogen transmission
No full textMany mammals are social. The most basic social behaviour is when the actions of one conspecific are directed toward another, what we call the ‘dyadic interaction’. Both intrinsic and extrinsic factors may affect an individual’s propensity to interact with other members of a population. I used a social cervid, elk (Cervus elaphus), as a model species to test the importance of intrinsic and extrinsic factors of sociality on dyadic interactions. Dyadic interactions not only form the basis for social structure and information transfer within a population, but are also routes of pathogen transmission. My objective in this thesis was thus twofold: to improve our understanding of sociobiology, but also to gain insight into how sociality may underlie the transmission of communicable wildlife disease. I used a hierarchical, autecological approach from DNA, through individual, dyad, group, subpopulation, and ultimately population to explore the effects of intrinsic factors (e.g., sex and pairwise genetic relatedness) and extrinsic factors (e.g., season, conspecific density, habitat, and elk group size) on sociality.
Elk in Riding Mountain National Park (RMNP), Manitoba, Canada, are exposed to the causal agent of bovine tuberculosis (Mycobacterium bovis; TB); however, spatial variation in apparent disease prevalence suggests that TB can only persist in one subpopulation within the Park. Using the natural RMNP system and a captive elk herd that I manipulated, I explored factors that influence interaction rates and durations (as a proxy for pathogen transmission) among elk.
Sexual segregation in elk results in seasonal and sex-based differences in interaction rate and duration; with interactions peaking in autumn-winter for both sexes. Female-female dyads interact more frequently than male-male dyads. However, male-male dyads interact for longer durations than do female-female dyads. Interaction rate and duration did not covary with pairwise relatedness. Conspecific density also had sex-specific results for interaction rate and duration. Whereas male-male dyadic interaction rates increase with density, female-female dyads increase until they reach a threshold and subsequently reduce their interaction rates at high density.
I observed density dependence in interaction rates in experimental trials and from field data. Furthermore, social networks revealed that social familiarity (i.e., heterogeneity of interactions) can be both frequency- and- density dependent depending on the strength of the relationship (i.e., number of repeat interactions). Density also affected the likelihood that an interaction would occur; however, this was modified by vegetation association used by elk.
My results reveal several ecological and evolutionary implications for information transfer and pathogen transmission. In particular, I show that seasonal inter-sex routes of transfer may exist and that transfer is likely to be density-dependent. Finally, I conclude that such transfer is modified by available resources
Core areas of habitat use : the influence of spatial scale of analysis on interpreting summer habitat selection by moose (Alces alces)
No full textI investigated summer habitat selection patterns within the home ranges of 60 GPS-collared
adult female moose (Alces alces) in northwestern Ontario. I developed a model that
identified the ‘summer’ period for moose and I suggest and test a new approach for
objectively delineating areas of intense use, or ‘core’ areas. Once summer and core areas
were established, I tested two competing hypotheses to identify differences in habitat
selected between the core areas and home range peripheries; (1) core areas represent
superior spatial configurations of habitats when compared to home range peripheries; and
(2) core areas are selected to contain a subset of ‘preferred’ forage species with higher
individual densities or a higher total density of all forage species than home range
peripheries. The study was conducted in 2 landscapes characterized by different
disturbance patterns created by different timber harvesting systems: modified “guidelines”
cut (MGC); and progressive, contiguous clear cut (PCC).
Moose move more and faster during the summer than the winter to exploit available forage.
I defined moose ‘summer’ as the period during the calendar year when an animal maintains
a rate of movement greater than the annual mean. Using a sub-sample (n=32) of animals
collared in 2000,1 determined 1 May 2000 as the median date for the ‘winter-summer’
transition (range: 2 April-24 May) and the median transition from ‘summer-winter’ was 25
August 2000 (range: 1 Aug-23 October).
Moose home ranges were designated using a 90% adaptive kernel. Within the home range,
moose devote a disproportionate amount of time to a fraction of the total area
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