Abstract
Animals are rarely distributed uniformly throughout their range, rather moving throughout their habitats in response to environmental variability, life history strategy, and individual preferences. Antarctic pack-ice represents one of the most dynamic marine habitats on Earth, undergoing large seasonal changes in extent, and being driven into constant motion by underlying currents. Such habitats are crucial for numerous pinniped species, but they may prevent them from foraging from a ‘central-place’ (as many do). While leopard seals are the most widespread of the Antarctic pack-ice seals, few studies have investigated their long-term spatial behaviour, or whether they maintain a central-place. Given individual movement drives spatial structure and trophic effects on prey populations, this is a substantial gap in our knowledge.
I sought to quantify leopard seal spatial behaviour along the West Antarctic Peninsula using satellite tracking technology, to determine whether leopard seals undertake large-scale north–south migration that follows the seasonal extension of the pack-ice edge, or whether they maintain a central-place strategy. Further, I quantified small-scale haul-out and swimming behaviour to assess whether travel driven by ice-flow and travel driven by conscious movement would differ. I hypothesised that leopard seals would migrate with the pack-ice edge, and in doing so would not maintain a central-place strategy.
I used Argos location data for 24 leopard seals fitted with satellite trackers and USNIC ice extent data to determine the distances of seals from the pack-ice edge and from their capture site, as well as the distances travelled while hauled-out and swimming.
I found all response variables varied over time, with sex having a significant effect on distance from the capture site and swimming distance. Most seals did not move the substantial distances needed for a large-scale migration which follows the pack-ice edge. The results suggest intersexual differences (potentially due to sexual dimorphism) and individual variability drove long-distance and small-scale movement in leopard seals.
While the leopard seals did not maintain a central-place strategy, their movement based on a trade-off between the pack-ice edge and the coastline suggests great flexibility, and future studies across other Antarctic sectors should investigate whether leopard seals are as flexible elsewhere in their range. Since leopard seals can have substantial top-down effects on multiple trophic levels, such information about their spatial behaviour is important for ecosystem-based fisheries modelling and future operations in Antarctic waters.
I sought to quantify leopard seal spatial behaviour along the West Antarctic Peninsula using satellite tracking technology, to determine whether leopard seals undertake large-scale north–south migration that follows the seasonal extension of the pack-ice edge, or whether they maintain a central-place strategy. Further, I quantified small-scale haul-out and swimming behaviour to assess whether travel driven by ice-flow and travel driven by conscious movement would differ. I hypothesised that leopard seals would migrate with the pack-ice edge, and in doing so would not maintain a central-place strategy.
I used Argos location data for 24 leopard seals fitted with satellite trackers and USNIC ice extent data to determine the distances of seals from the pack-ice edge and from their capture site, as well as the distances travelled while hauled-out and swimming.
I found all response variables varied over time, with sex having a significant effect on distance from the capture site and swimming distance. Most seals did not move the substantial distances needed for a large-scale migration which follows the pack-ice edge. The results suggest intersexual differences (potentially due to sexual dimorphism) and individual variability drove long-distance and small-scale movement in leopard seals.
While the leopard seals did not maintain a central-place strategy, their movement based on a trade-off between the pack-ice edge and the coastline suggests great flexibility, and future studies across other Antarctic sectors should investigate whether leopard seals are as flexible elsewhere in their range. Since leopard seals can have substantial top-down effects on multiple trophic levels, such information about their spatial behaviour is important for ecosystem-based fisheries modelling and future operations in Antarctic waters.
| Original language | English |
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| Publication status | Published - Oct 2013 |