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Identifying Space Use at Foraging Arena Scale within the Home Ranges of Large Herbivores.

Owen-Smith N, Martin J - PLoS ONE (2015)

Bottom Line: We compared how these herbivore species responded to seasonal variation in food resources and how they differed in their spatial patterns of resource utilization.The amalgamated extent of the foraging arenas exploited by sable herds amounted to 12-30 km2, compared with 22-100 km2 for the zebra herds.Thereby it helps forge links between behavioural ecology, movement ecology and population ecology.

View Article: PubMed Central - PubMed

Affiliation: Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Wits, South Africa.

ABSTRACT
An intermediate spatiotemporal scale of food procurement by large herbivores is evident within annual or seasonal home ranges. It takes the form of settlement periods spanning several days or weeks during which foraging activity is confined to spatially discrete foraging arenas, separated by roaming interludes. Extended by areas occupied for other activities, these foraging arenas contribute towards generating the home range structure. We delineated and compared the foraging arenas exploited by two African large herbivores, sable antelope (a ruminant) and plains zebra (a non-ruminant), using GPS-derived movement data. We developed a novel approach to specifically delineate foraging arenas based on local change points in distance relative to adjoining clusters of locations, and compared its output with modifications of two published methods developed for home range estimation and residence time estimation respectively. We compared how these herbivore species responded to seasonal variation in food resources and how they differed in their spatial patterns of resource utilization. Sable antelope herds tended to concentrate their space use locally, while zebra herds moved more opportunistically over a wider set of foraging arenas. The amalgamated extent of the foraging arenas exploited by sable herds amounted to 12-30 km2, compared with 22-100 km2 for the zebra herds. Half-day displacement distances differed between settlement periods and roaming interludes, and zebra herds generally shifted further over 12h than sable herds. Foraging arenas of sable herds tended to be smaller than those of zebra, and were occupied for period twice as long, and hence exploited more intensively in days spent per unit area than the foraging arenas of zebra. For sable both the intensity of utilization of foraging arenas and proportion of days spent in foraging arenas relative to roaming interludes declined as food resources diminished seasonally, while zebra showed no seasonal variation in these metrics. Identifying patterns of space use at foraging arena scale helps reveal mechanisms generating the home range extent, and in turn the local population density. Thereby it helps forge links between behavioural ecology, movement ecology and population ecology.

No MeSH data available.


Seasonal trends in movement metrics representing the bimonthly means of the utilization intensity, in days spent per unit area, of foraging arenas (A), the proportion of days within foraging arenas compared with roaming interludes (B), and the compound intensity of use calculated as the product of days of occupation and utilization intensity (C).Circles indicate points for individual sable herds and square are points for individual zebra herds, while lines indicate mean values averaged over the sable herds (solid line) and over the zebra herds (dashed line).
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pone.0128821.g009: Seasonal trends in movement metrics representing the bimonthly means of the utilization intensity, in days spent per unit area, of foraging arenas (A), the proportion of days within foraging arenas compared with roaming interludes (B), and the compound intensity of use calculated as the product of days of occupation and utilization intensity (C).Circles indicate points for individual sable herds and square are points for individual zebra herds, while lines indicate mean values averaged over the sable herds (solid line) and over the zebra herds (dashed line).

Mentions: Correspondingly, exploitation intensities averaged over all herds tended to be greater for sable than for zebra through all seasons, despite quite wide variation among individual herds representing these ungulate species (Fig 9A). For sable, exploitation intensities decreased from the late wet season months through the dry season. For zebra, seasonal variation was slight and two of the collared zebra herds showed substantially lowered intensities of exploitation during the early dry season months. The proportion of days spent within FAs decreased for sable through the latter part of the dry season, while for zebra a more complex pattern was shown, with lowest settled proportions during the initial months of the dry season and during the transitional months ending the late dry season (Fig 9B). The compound utilization intensity, i.e. the product of exploitation intensities within FAs and the proportion of time spent settled with FAs, showed a clear downward trend through the dry season for sable, while zebra showed little seasonal variation in this derived measure (Fig 9C). Notably, the over-riding influence came from changes in utilization intensity rather than in the settlement proportion.


Identifying Space Use at Foraging Arena Scale within the Home Ranges of Large Herbivores.

Owen-Smith N, Martin J - PLoS ONE (2015)

Seasonal trends in movement metrics representing the bimonthly means of the utilization intensity, in days spent per unit area, of foraging arenas (A), the proportion of days within foraging arenas compared with roaming interludes (B), and the compound intensity of use calculated as the product of days of occupation and utilization intensity (C).Circles indicate points for individual sable herds and square are points for individual zebra herds, while lines indicate mean values averaged over the sable herds (solid line) and over the zebra herds (dashed line).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4466150&req=5

pone.0128821.g009: Seasonal trends in movement metrics representing the bimonthly means of the utilization intensity, in days spent per unit area, of foraging arenas (A), the proportion of days within foraging arenas compared with roaming interludes (B), and the compound intensity of use calculated as the product of days of occupation and utilization intensity (C).Circles indicate points for individual sable herds and square are points for individual zebra herds, while lines indicate mean values averaged over the sable herds (solid line) and over the zebra herds (dashed line).
Mentions: Correspondingly, exploitation intensities averaged over all herds tended to be greater for sable than for zebra through all seasons, despite quite wide variation among individual herds representing these ungulate species (Fig 9A). For sable, exploitation intensities decreased from the late wet season months through the dry season. For zebra, seasonal variation was slight and two of the collared zebra herds showed substantially lowered intensities of exploitation during the early dry season months. The proportion of days spent within FAs decreased for sable through the latter part of the dry season, while for zebra a more complex pattern was shown, with lowest settled proportions during the initial months of the dry season and during the transitional months ending the late dry season (Fig 9B). The compound utilization intensity, i.e. the product of exploitation intensities within FAs and the proportion of time spent settled with FAs, showed a clear downward trend through the dry season for sable, while zebra showed little seasonal variation in this derived measure (Fig 9C). Notably, the over-riding influence came from changes in utilization intensity rather than in the settlement proportion.

Bottom Line: We compared how these herbivore species responded to seasonal variation in food resources and how they differed in their spatial patterns of resource utilization.The amalgamated extent of the foraging arenas exploited by sable herds amounted to 12-30 km2, compared with 22-100 km2 for the zebra herds.Thereby it helps forge links between behavioural ecology, movement ecology and population ecology.

View Article: PubMed Central - PubMed

Affiliation: Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Wits, South Africa.

ABSTRACT
An intermediate spatiotemporal scale of food procurement by large herbivores is evident within annual or seasonal home ranges. It takes the form of settlement periods spanning several days or weeks during which foraging activity is confined to spatially discrete foraging arenas, separated by roaming interludes. Extended by areas occupied for other activities, these foraging arenas contribute towards generating the home range structure. We delineated and compared the foraging arenas exploited by two African large herbivores, sable antelope (a ruminant) and plains zebra (a non-ruminant), using GPS-derived movement data. We developed a novel approach to specifically delineate foraging arenas based on local change points in distance relative to adjoining clusters of locations, and compared its output with modifications of two published methods developed for home range estimation and residence time estimation respectively. We compared how these herbivore species responded to seasonal variation in food resources and how they differed in their spatial patterns of resource utilization. Sable antelope herds tended to concentrate their space use locally, while zebra herds moved more opportunistically over a wider set of foraging arenas. The amalgamated extent of the foraging arenas exploited by sable herds amounted to 12-30 km2, compared with 22-100 km2 for the zebra herds. Half-day displacement distances differed between settlement periods and roaming interludes, and zebra herds generally shifted further over 12h than sable herds. Foraging arenas of sable herds tended to be smaller than those of zebra, and were occupied for period twice as long, and hence exploited more intensively in days spent per unit area than the foraging arenas of zebra. For sable both the intensity of utilization of foraging arenas and proportion of days spent in foraging arenas relative to roaming interludes declined as food resources diminished seasonally, while zebra showed no seasonal variation in these metrics. Identifying patterns of space use at foraging arena scale helps reveal mechanisms generating the home range extent, and in turn the local population density. Thereby it helps forge links between behavioural ecology, movement ecology and population ecology.

No MeSH data available.