Ecology of Norway Rats (Rattus Norvegicus) in relation to conservation and management of seabirds on Kiska Island, Aleutian Islands, Alaska 2005-2006

Eggleston, Cari (2010) Ecology of Norway Rats (Rattus Norvegicus) in relation to conservation and management of seabirds on Kiska Island, Aleutian Islands, Alaska 2005-2006. Masters thesis, Memorial University of Newfoundland.

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Abstract

Historical invasions by introduced species into formerly pristine ecosystems present a case where damage and change must often be measured indirectly. Long-term monitoring of demographic parameters has been used to infer trends of the auklet colony at Sirius Point, Kiska Island Alaska in relation to predation by introduced Norway rats (Rattus norvegicus). In 2001 and 2002 the auklet colony experienced the lowest reproductive success ever recorded for auklets. Norway rats have been suggested as the cause for auklet reproductive failure due to anecdotal evidence and incidental sign collected at the colony. The first part of my study was to investigate Least Auklet population trends post reproductive failure at Kiska. I found that annual adult local survival estimates for 2002-2005 steadily declined to below 0.8 while reproductive success rebounded to normal levels (54% in 2006). Overall productivity was significantly lower at an island with rats (Kiska) as compared to islands without rats (Kasatochi: z = 7.24, df = 6, P < 0.0001, Buldir: z = 5.58, df = 6, P < 0.0001). -- The next part of my study aimed to go beyond the previous approach centered on auklet monitoring and focus on Norway rat activity at the auklet colony as well as estimate rat density and develop a method to measure relative abundance. In 2006 radio tracking was used to quantify Norway rat home ranges and movements located near the center of the auklet colony. Rat home range estimates varied from an average of 7713 ± 1978 m² for male rats to 3169 ± 244 m² for female rats. Compared to other islands, home ranges were smaller and density estimates, 12.75 rats/ha, were higher at Sirius Point, with rats living largely underground in the lava dome or tunneling through grass. Rat distribution was patchy - not all habitat types were used equally. -- Three non-invasive index methods (chew sticks, wax blocks and tracking tunnels) were tested to measure Norway rat abundance. Rats were attracted to all indexing methods tested in 2005 and 2006. Fortunately, the most successful method tested, peanut butter flavored wax blocks, also was an easy and inexpensive method to apply in the terrain at Sirius Point, Kiska Island. This method will likely prove to be a good choice to monitor fluctuations in rat populations annually at seabird colonies. Taken together, the results of my thesis work showed that Norway rat activity, while difficult to track and monitor, can be measured using novel methodology that will ultimately contribute to management and conservation of Aleutian Island ecosystems.

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