I developed a spatially explicit individual-based model (IBM) to capture the dynamic
behavioral interaction between a fierce predator (killer whale, Orcinus orca) and a clever
prey (dusky dolphin, Lagenorhynchus obscurus), and to answer the ultimate question of
costs vs. benefits for dusky dolphins when making anti-predator decisions. Specifically, I
was interested in calculating time/distance budgets for dusky dolphins in the
presence/absence of killer whales and the presence/absence of movement and behavioral
rules, which presumably evolved in response to spatial and temporal variations in
predation risk. Results reveal that dusky dolphins rest less, travel more and have
reduced foraging time when killer whales are present. These effects are more
pronounced with increased presence of killer whales. The model suggests that a strong
reason favoring the adoption of short and long-term anti-predator mechanisms is
increased survival resulting from decreased encounters with killer whales. Further, a
mother with calf rests less and travels more when killer whales are present relative to a
dolphin without calf. However, a mother with calf on average, flee shorter distances and
have fewer encounters with killer whales than a dolphin without calf. Thus, despite ecological costs, it makes evolutionary sense for dusky dolphins to adopt anti-predator
rules. Bioenergetic consequences for dusky dolphins with and without calf were
estimated as total energetic costs and foraging calories lost due to low/high presence of
killer whales. I calculated total energy costs as: Foraging costs (FC) Locomotor costs
(LC) (Travel) or LC (Travel) LC (Flee) based on the absence, as well as low/high
presence of killer whales. Foraging costs contributed significantly to total energetic costs
estimated. Travel costs are minimal owing to proximity to deep waters. The total energy
costs were not significantly higher from low or high presence of killer whales for mother
with calf, but increases by about 90 kcal/day for a dusky without calf. However, I
estimate foraging calories lost due to increased killer whale presence is almost 5 times
more for mother with calf. Therefore, it might be important to consider indirect
predation risk effects by social type in future studies on animal bioenergetics.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-329 |
| Date | 16 January 2010 |
| Creators | Srinivasan, Mridula |
| Contributors | Wursig, Bernd |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation |
| Format | application/pdf |
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