Movement Ecology

Limited influence of stream networks on the terrestrial movements of three wetland-dependent frog species

by Martin Westgate

with Don Driscoll and David Lindenmayer. In press with Biological Conservation.

Quantifying functional connectivity is essential for understanding factors that limit or promote animal dispersal in... more Quantifying functional connectivity is essential for understanding factors that limit or promote animal dispersal in fragmented landscapes. Topography is a major factor influencing the movement behaviour of many animal species, and therefore the extent of functional connectivity between habitat patches. For pond-breeding frogs, areas of low topographic relief (such as streams or drainage lines) offer damp microhabitats that can facilitate movement through otherwise dry landscapes. However, the extent of topographic bias of frog movements has rarely been quantified. We used a replicated study to compare captures in high- and low-relief transects, for three species from a pond-breeding frog community in southeastern Australia. We captured frogs significantly more often on low-relief transects. However, capture rates decreased with increasing distance from water at similar rates on both high-relief and low-relief transects, and we observed few differences between adult and juvenile movements. Our results suggest that although low-relief drainage lines are important for the pond-breeding frogs in question, ecologists and landscape managers should not discount the role of high-relief locations. Because low-relief drainage lines represent a low proportion of the pond margin, >90% of movements are likely to occur across high-relief locations. Therefore, for the species that we studied, buffer zones designed to conserve only hydrological networks would provide insufficient protection of frequently used pond margins, while drainage lines are unlikely to act as vital networks facilitating connectivity between breeding ponds. Our study suggests that movement across slopes may be most important for facilitating functional connectivity.

From migration to nomadism: movement variability in a northern ungulate across its latitudinal range

by Luca Börger

Ecological Applications (in print) Co-authored with Navinder Singh (first author), Nils Bunnefeld, Holger Detki, and Goran Ericsson.

This is the first proper application of my net-squared displacement approach for modelling animal movements (Borger & Fryxell 2012).
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Understanding the causes and consequences of animal movements is of fundamental biological interest because any... more Understanding the causes and consequences of animal movements is of fundamental biological interest because any alteration in movement can have direct and indirect effects on ecosystem structure and function. It is also crucial for assisting spatial wildlife management under variable environmental change scenarios. Recent research has highlighted the need of quantifying individual variability in movement behavior and how it is generated by interactions between individual requirements and environmental conditions, to understand the emergence of population level patterns. Using a multi-annual movement dataset of 213 individual moose (Alces alces) across a latitudinal gradient (from 56° to 67° N) that spans over 1,100 km of varying environmental conditions, we analyze the differences in individual and population level movements. We tested the effect of climate, risk and human presence in the landscape on moose movements. The variation in these factors explained the existence of multiple movements (migration, nomadism, dispersal, sedentary) among individuals and seven populations. Hence, heterogeneity in the immediate environment can result in multiple movements within a species. Population differences were primarily related to latitudinal variation in snow depth and road density. Individuals showed both fixed and flexible behaviors across years, and were less likely to migrate with age in interaction with snow and roads. For the predominant movement strategy, migration, the distance, timing and duration at all latitudes varied between years. Males traveled longer distances and began migrating earlier in spring than females. Our study provides strong quantitative evidence for the dynamics of animal movements in response to changes in environmental conditions along with varying risk from human influence across the landscape. For moose, given its wide distributional range, changes in the distribution and migratory behavior are expected under future warming scenarios.

Push and Pull Factors Affecting Migration from Bicol Region to Metro Manila

by Mickey Eva

By: Jose Emmanuel Micael Miguel-Eva VIII (ed.), Karissa Dumaraog, Lorenzo Galvez, Anne Lorraine Garcia, Eugene Lanuza, Ryan Malit and Marian Marigmen for Geog 119 (Geography of Movement), a class under Prof. Mylene De Guzman of the Department at the University of the Philippines in Quezon City, Philippines

К реконструкции лодки из энеолитического могильника Бузан-3 в Ингальской долине (интерпретация с использованием данных этнографии)

by Vladimir Adaev

Передвижение человека по местности как важный фактор этноэкологических исследований

by Vladimir Adaev

A model-driven approach to quantify migration patterns: individual, regional and yearly differences

by Luca Börger

Journal of Animal Ecology (2011). Co-authored with Nils Bunnefeld (first author), Bram van Moorter, Christer M. Rolandsen, Holger Dettki, Erling Johan Solberg, and Goran Ericsson.

This is an extension of my squared displacement modelling approach, published in the book chapter Borger & Fryxell (2012, Oxford University Press), to include the case of migration. Beware, this publication on migration is somewhat preliminary in several aspects. Before using it on migration or other data I strongly suggest to refer to the original presentation of the method in Borger & Fryxell (2012, OUP), as it is considerably more rigorous and markedly improved.
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1. Animal migration has long intrigued scientists and wildlife managers alike, yet migratory species face increasing... more 1. Animal migration has long intrigued scientists and wildlife managers alike, yet migratory species face increasing challenges because of habitat fragmentation, climate change and over-exploitation. Central to the understanding migratory species is the objective discrimination between migratory and nonmigratory individuals in a given population, quantifying the timing, duration and distance of migration and the ability to predict migratory movements.

2. Here, we propose a uniform statistical framework to (i) separate migration from other movement behaviours, (ii) quantify migration parameters without the need for arbitrary cut-off criteria and (iii) test predictability across individuals, time and space.

3. We first validated our novel approach by simulating data based on established theoretical movement patterns. We then formulated the expected shapes of squared displacement patterns as nonlinear models for a suite of movement behaviours to test the ability of our method to distinguish between migratory movement and other movement types.

4. We then tested our approached empirically using 108 wild Global Positioning System (GPS)-collared moose Alces alces in Scandinavia as a study system because they exhibit a wide range of movement behaviours, including resident, migrating and dispersing individuals, within the same population. Applying our approach showed that 87% and 67% of our Swedish and Norwegian subpopulations, respectively, can be classified as migratory.

5. Using nonlinear mixed effects models for all migratory individuals we showed that the distance, timing and duration of migration differed between the sexes and between years, with additional individual differences accounting for a large part of the variation in the distance of migration but not in the timing or duration. Overall, the model explained most of the variation (92%) and also had high predictive power for the same individuals over time (69%) as well as between study populations (74%).

6. The high predictive ability of the approach suggests that it can help increase our understanding of the drivers of migration and could provide key quantitative information for understanding and
managing a broad range of migratory species.

Quantifying the difference between animal movements and Brownian motion: Why do we still fail?

by Luca Börger

Bulletin of the Ecological Society of America (2007). Coauthored with Ben Dalziel and John Fryxell and presented at the 92nd ESA Meeting in San Jose.

Preliminary results - full work later published in the Journal Ecology Letters (2008).

Despite considerable research we still lack a satisfactory conceptual model of animal movement behavior. We offer a... more Despite considerable research we still lack a satisfactory conceptual model of animal movement behavior. We offer a novel approach to this problem by combining statistical and mathematical modeling approaches. First, we present an integrated statistical framework for the analysis of animal space use data. Using data from mammal and bird species we address topics ranging from the allocation of field resources to data collection, to a spatially explicit decomposition of the variance in home range size into components due to variation in temporal, spatial, and individual-level processes. Second, we compare mathematical models of home range behavior, showing that most actually fail to accommodate real animal movement data. This is caused by an emphasis on the entropy present in movement data while ignoring its higher order properties. Traditionally, animal movement has been modeled as an essentially random process, with added structure created by dependence on previously visited locations or attraction to particular habitats. We demonstrate, however, that these models predict that an animal's range will expand continually, which is contrary to home range behavior. The size of home ranges is often extremely small relative to the velocity of the animal. None of the existing modeling approaches predict the formation of stationary home ranges as an emergent property of animal movement paths. We propose possible solutions and conclude that a unified view of the progress in both areas represents an exciting opportunity for future field-based and theoretical studies.

Effects of sampling regime on the mean and variance of home range size estimates

by Luca Börger

Journal of Animal Ecology (2006); co-authored with N. Franconi, G. De Michele, A. Gantz, F. Meschi, A. Manica, S. Lovari, and T. Coulson.

1. Although the home range is a fundamental ecological concept, there is considerable debate over how it is best... more 1. Although the home range is a fundamental ecological concept, there is considerable debate over how it is best measured. There is a substantial literature concerning the precision and accuracy of all commonly used home range estimation methods; however, there has been considerably less work concerning how estimates vary with sampling regime, and how this affects statistical inferences.

2. We propose a new procedure, based on a variance components analysis using generalized mixed effects models to examine how estimates vary with sampling regime.

3. To demonstrate the method we analyse data from one study of 32 individually marked roe deer and another study of 21 individually marked kestrels. We subsampled these data to simulate increasingly less intense sampling regimes, and compared the performance of two kernel density estimation (KDE) methods, of the minimum convex polygon (MCP) and of the bivariate ellipse methods.

4. Variation between individuals and study areas contributed most to the total variance in home range size. Contrary to recent concerns over reliability, both KDE methods were remarkably efficient, robust and unbiased: 10 fixes per month, if collected over a standardized number of days, were sufficient for accurate estimates of home range size. However, the commonly used 95% isopleth should be avoided; we recommend using isopleths between 90 and 50%.

5. Using the same number of fixes does not guarantee unbiased home range estimates: statistical inferences differ with the number of days sampled, even if using KDE methods.

6. The MCP method was highly inefficient and results were subject to considerable and unpredictable biases. The bivariate ellipse was not the most reliable method at low sample sizes.

7. We conclude that effort should be directed at marking more individuals monitored over long periods at the expense of the sampling rate per individual. Statistical results are reliable only if the whole sampling regime is standardized. We derive practical guidelines for field studies and data analysis.

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Updates:
Featured in the Virtual Issue "Biotelemetry and Biologging" (2008) edited by Graeme Hays.
http://www.journalofanimalecology.org/view/0/virtualissue1.html

Among the top 10 most downloaded papers from the Journal of Animal Ecology for the first year after publication.

Among the top 5 cited papers in Journal of Animal Ecology published over the last 5 years (Nov 2010).

Cited 100+ times on WOS (Jan 2012).

SPOSTAMENTI DELL’ISTRICE IN RELAZIONE AL SITO DI TANA

by Luca Börger

Hystrix - The Italian Journal of Mammalogy (2003) Conference proceedings co-authored with Lisa Monetti (first author), Alessandro Massolo, Andrea Sforzi and Sandro Lovari

USO DELLO SPAZIO NELL’ISTRICE (Hystrix cristata L., 1758) IN UN’AREA COSTIERA MEDITERRANEA

by Luca Börger

MSc thesis (2002; University of Pisa, Italy)

This research is part of an extensive research project of the University of Siena, started 1990, on the porcupine, a... more This research is part of an extensive research project of the University of Siena, started 1990, on the porcupine, a protected species of special national interest, whose biology and ecology is scarcely known. Three study areas were located in the Province of Siena and one in the Maremma Regional Park In the last one this research has been carried out, from 1997 to 2002, in two stages, the first one (1997-2000) in the Mediterranean scrub wood, the second (2000-2002) in the pine wood. Porcupine space use patterns and the biotic and abiotic factors affecting them have been studied by means of radio tracking. Fifty-six porcupines have been trapped; datas of radiotagged animals tracked for at least 4 consecutive months (20 animals: 11 females, 9 males) have been analysed. Radiotracking sessions lasted half night each one, equally spaced on yearly basis, with 15 sessions per month. In addition, during daylight, den sites of radiotagged animals were located. Yearly home range sizes were bigger than in all other study areas: in the scrubwood (N=8; median) MCP 100% 323.5 ha, MCP 90% 241.5 ha, kernel 95% 164,7 ha; in the pinewood (N=2) MCP 100% 704.1 ha, MCP 90% 477.3 ha, kernel 95% 405.7 ha. Male home range sizes were bigger than female ranges although the difference was not significant. Support for the body-size hypotheses of home range size (McNab 1963) has not been found, by contrast, the habitat productivity hypotheses (Harestad&Bunnel 1979) explains well differences in home range size with the other study areas. Home range sizes were related to the quantity of wet areas in the home range, as well as to habitat heterogeneity. Seasonal and monthly home range size varied greatly and appeared to be related to the dry summer period, mean monthly temperature and monthly precipitation. The porcupines used a high number of underground burrows (“setts”), up to 9 different setts/individual, apparently constituted by one or few main sett(s) and a variable number of outlier setts, perhaps related to the foraging sites locations. Every sett seemed to be used by one reproductive pair with, if present, the offspring. No contemporary use of the same sett by two adult males or two adult females was found, only single animals or male-female pairs, in the latter case always the same pairs, though different females used the same setts in different days. Males and females of the pairs were strictly associated all year long not inside the dens but also during activity outside the sett, with a high degree of home range overlap. One pair, which certainly reproduced, has been intensively monitored for 25 months: the association and coordination of the spacing behaviour was very high; apparently the male was more involved in pair-bond maintenance, in addition some evidence of male parental care has been collected. Altogether, evidence supporting the hypotheses of porcupine monogamy has been collected, this case is discussed in the context of the distribution of mammal monogamy.

EFFETTI DEL PROTOCOLLO DI CAMPIONAMENTO SULLA MEDIA E VARIANZA DELLE STIME DEGLI HOME RANGE: UN NUOVO METODO DI ANALISI

by Luca Börger

Hystrix - The Italian Journal of Mammalogy (2005) Conference proceedings co-authored with N. Franconi, G. De Michele, A. Gantz, F. Meschi, A. Manica, S. Lovari, and T. Coulson. Preliminary results - full work later published in the Journal of Animal Ecology.

Are there general mechanisms of animal home range behaviour? A review and prospects for future research

by Luca Börger

Ecology Letters (2008); co-authored with B. D. Dalziel, and J. M. Fryxell.

Home range behaviour is a common pattern of space use, having fundamental consequences for ecological processes.... more 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.

Multiple movement modes by large herbivores at multiple spatio-temporal scales

by Luca Börger

Proceedings of the National Academy of Sciences (2008); co-authored with J.M. Fryxell (first author), M. Hazell, B. D. Dalziel, D. T. Haydon, J. M. Morales, T. McIntosh, and R.C. Rosatte.

Recent theory suggests that animals should switch facultatively among canonical movement modes as a complex function... more Recent theory suggests that animals should switch facultatively among canonical movement modes as a complex function of internal state, landscape characteristics, motion capacity, and navigational capacity. We tested the generality of this paradigm for free-ranging elk (Cervus elaphus) over 5 orders of magnitude in time (minutes to years) and space (meters to 100 km). At the coarsest spatiotemporal scale, elk shifted from a dispersive to a home-ranging phase over the course of 1–3 years after introduction into a novel environment. At intermediate spatiotemporal scales, elk continued to alternate between movement modes. During the dispersive phase, elk alternated between encamped and exploratory modes, possibly linked to changes in motivational goals from foraging to social bonding. During the home-ranging phase, elk movements were characterized by a complex interplay between attraction to preferred habitat types and memory of previous movements across the home-range. At the finest temporal and spatial scale, elk used area-restricted search while browsing, interspersed with less sinuous paths when not browsing. Encountering a patch of high-quality food plants triggered the switch from one mode to the next, creating biphasic movement dynamics that were reinforced by local resource heterogeneity. These patterns suggest that multiphasic structure is fundamental to the movement patterns of elk at all temporal and spatial scales tested.

Memory keeps you at home: a mechanistic model for home range emergence

by Luca Börger

Oikos (2009). Coauthored with Bram Van Moorter (first author), Darcy Visscher, Simon Benhamou, Mark Boyce, Jean-Michel Gaillard.

Despite its central place in animal ecology no general mechanistic movement model with an emergent home-range pattern... more Despite its central place in animal ecology no general mechanistic movement model with an emergent home-range pattern has yet been proposed. Random walk models, which are commonly used to model animal movement, show diffusion instead of a bounded home range and therefore require special modifications. Current approaches for mechanistic modeling of home ranges apply only to a limited set of taxa, namely territorial animals and/or central place foragers. In this paper we present a more general mechanistic movement model based on a biased correlated random walk, which shows the potential for home-range behavior. The model is based on an animal tracking a dynamic resource landscape, using a biologically plausible two-part memory system, i.e. a reference- and a working-memory. Our results show that by adding these memory processes the random walker produces home-range behavior as it gains experience, which also leads to more efficient resource use. Interestingly, home-range patterns, which we assessed based on home-range overlap and increase in area covered with time, require the combined action of both memory components to emerge. Our model has the potential to predict home-range size and can be used for comparative analysis of the mechanisms shaping home-range patterns.

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Update:
Evaluated by Faculty of 1000 Biology (level 3 - Recommended) in 2009:
http://f1000biology.com/article/id/1161966/evaluation

Could you please phrase “home range” as a question?

by Luca Börger

Journal of Mammalogy (accepted). Co-authored with John Fieberg (first author).

This is a pre-print. Publication is scheduled for Aug 2012 as part of a special issue on animal home ranges (editor Roger Powell).
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Statisticians frequently voice concern that their interactions with applied researchers start only after data have... more Statisticians frequently voice concern that their interactions with applied researchers start only after data have been collected. The same can be said for our experience with home-range studies. Too often, conversations about home range begin with questions concerning estimation methods, smoothing parameters, or the nature of autocorrelation. More productive efforts start by asking good (and interesting) research questions; once these questions are defined, it becomes possible to ask how various design and analysis strategies influence one’s ability to answer these questions. With this process in mind, we address key sample design and data analysis issues related to the topic of home range. The impact of choosing a particular home-range estimator (e.g., minimum convex polygon, kernel density estimator, local convex hull) will be question dependent, and for some problems other movement or use-based metrics (e.g., mean step lengths, time spent in particular areas) may be worthy of consideration. Thus, we argue the need for more question-driven and focused research and for clearly distinguishing the biological concept of an animal’s home range from the statistical quantities one uses to investigate this concept. For comparative studies, it is important to standardize sampling regimes and estimation methods as much as possible, and to pay close attention to missing data issues. More attention should also be given to temporally changing space-use patterns, with biologically meaningful time periods (e.g., life history stages) used to define sampling periods. Lastly, we argue the need for closer connections between theoretical and empirical researchers. Advances in ecological theory, and its application to natural resources management, will require carefully designed research studies to test theoretical predictions from more mechanistic modeling approaches.

Sampling rate and misidentification of Lévy and non-Lévy movement paths: reply

by Edward Codling

Turn designation, sampling rate and the misidentification of power laws in movement path data using maximum likelihood estimates

by Edward Codling

Group navigation and the "many-wrongs principle" in models of animal movement

by Edward Codling

Sampling rate effects on measurements of correlated and biased random walks

by Edward Codling

Random walk models for the movement and recruitment of reef fish larvae

by Edward Codling