The Decline of the Southern Resident Population of Killer Whales: A Two-Part Analysis
The southern resident population of killer whales declined dramatically in the late 1990s. The number of animals in the population dropped from 97 in 1996 to 78 in 2001, a 20% decline in just five years. Although the reasons for this decline are unknown, external factors such as contaminant exposure...
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ftdukeunivdsp:oai:localhost:10161/235 2023-11-12T04:20:16+01:00 The Decline of the Southern Resident Population of Killer Whales: A Two-Part Analysis Abbott, Kelsey Crowder, Larry B 2004 270832 bytes application/pdf https://hdl.handle.net/10161/235 en_US eng https://hdl.handle.net/10161/235 Killer whale (Orcinus orca) Population Decline Visual Assessment Master's project 2004 ftdukeunivdsp 2023-10-17T09:44:22Z The southern resident population of killer whales declined dramatically in the late 1990s. The number of animals in the population dropped from 97 in 1996 to 78 in 2001, a 20% decline in just five years. Although the reasons for this decline are unknown, external factors such as contaminant exposure, vessel interference, and low prey availability may contribute to the poor health and eventual mortality of the animals. My analysis examines two trends in southern resident mortality. Part 1 uses the percentage of mature males in a population as a surrogate for adult survival and compares the percentage of mature males in the southern resident population versus that of other populations of killer whales. My results indicate that the proportion of the southern resident population that is adult males is significantly lower than the percentage of adult males in the fourteen other populations sampled. I speculate that the high contaminant levels and increased nutritional stress of southern resident males led to this male-biased mortality. In the second part, I develop a method for visually assessing killer whale body condition using photographs. Through 30 years of study, ten southern residents died as a result of emaciation. Of these, two individuals were characterized as “extremely thin” prior to death and four were described as “very thin.” Preliminary results indicate that conditions described as worse than “thin” predict mortality. However, body condition of all members of the population fluctuates over time, suggesting that some population-wide factor such as prey availability may influence body condition. Both of these techniques enable managers to track changes in the population over time, thus advancing our understanding of the fluctuating population dynamics of the southern resident community. Master Thesis Killer Whale Orca Orcinus orca Killer whale Duke University Libraries: DukeSpace |
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Open Polar |
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Duke University Libraries: DukeSpace |
op_collection_id |
ftdukeunivdsp |
language |
English |
topic |
Killer whale (Orcinus orca) Population Decline Visual Assessment |
spellingShingle |
Killer whale (Orcinus orca) Population Decline Visual Assessment Abbott, Kelsey The Decline of the Southern Resident Population of Killer Whales: A Two-Part Analysis |
topic_facet |
Killer whale (Orcinus orca) Population Decline Visual Assessment |
description |
The southern resident population of killer whales declined dramatically in the late 1990s. The number of animals in the population dropped from 97 in 1996 to 78 in 2001, a 20% decline in just five years. Although the reasons for this decline are unknown, external factors such as contaminant exposure, vessel interference, and low prey availability may contribute to the poor health and eventual mortality of the animals. My analysis examines two trends in southern resident mortality. Part 1 uses the percentage of mature males in a population as a surrogate for adult survival and compares the percentage of mature males in the southern resident population versus that of other populations of killer whales. My results indicate that the proportion of the southern resident population that is adult males is significantly lower than the percentage of adult males in the fourteen other populations sampled. I speculate that the high contaminant levels and increased nutritional stress of southern resident males led to this male-biased mortality. In the second part, I develop a method for visually assessing killer whale body condition using photographs. Through 30 years of study, ten southern residents died as a result of emaciation. Of these, two individuals were characterized as “extremely thin” prior to death and four were described as “very thin.” Preliminary results indicate that conditions described as worse than “thin” predict mortality. However, body condition of all members of the population fluctuates over time, suggesting that some population-wide factor such as prey availability may influence body condition. Both of these techniques enable managers to track changes in the population over time, thus advancing our understanding of the fluctuating population dynamics of the southern resident community. |
author2 |
Crowder, Larry B |
format |
Master Thesis |
author |
Abbott, Kelsey |
author_facet |
Abbott, Kelsey |
author_sort |
Abbott, Kelsey |
title |
The Decline of the Southern Resident Population of Killer Whales: A Two-Part Analysis |
title_short |
The Decline of the Southern Resident Population of Killer Whales: A Two-Part Analysis |
title_full |
The Decline of the Southern Resident Population of Killer Whales: A Two-Part Analysis |
title_fullStr |
The Decline of the Southern Resident Population of Killer Whales: A Two-Part Analysis |
title_full_unstemmed |
The Decline of the Southern Resident Population of Killer Whales: A Two-Part Analysis |
title_sort |
decline of the southern resident population of killer whales: a two-part analysis |
publishDate |
2004 |
url |
https://hdl.handle.net/10161/235 |
genre |
Killer Whale Orca Orcinus orca Killer whale |
genre_facet |
Killer Whale Orca Orcinus orca Killer whale |
op_relation |
https://hdl.handle.net/10161/235 |
_version_ |
1782336306460753920 |