The Potential Efficacy of Spotlight Hunting to Control Feral Cats in Mariana Crow Nesting Areas

Sarah Faegre SEFS 520 Spring 2014 Rota

The Mariana Crow (Aga; kubaryi)

•Endemic to Rota and

• Extirpated from Guam by the Brown Tree Snake

• Common on Rota until the late 1990s

•60% population decline between 1999 and 2010

•Critically endangered; <50 pairs

Mariana Crow Life History

• First reproduction at ~2 years • Senescence ~ 12 years • 1-2 chicks / successful nest • Extended parental care (8 month average)

Suspected Causes of Current Decline • Disease – no evidence • Nest failure – little evidence • Human persecution – little evidence • Inbreeding – never studied • Habitat degradation – never studied • Feral cats – recent evidence Climbing Trees and Finding Nests

Colorbanding and Radio-tagging

Radio-tracking

• Mariana Crows have low juvenile and adult survivorship compared to stable Corvid populations (based on colorband resights)

• 9 of 31 radio-tagged crows were killed by feral cats

• PVA suggests that increasing adult survivorship is the best management strategy

So, we need to control feral cats in habitat used by adult crows. But how? Spotlight Hunting:

• More cats per unit effort • Only removes cats on roads

Live trapping:

• Remove cats from targeted areas of jungle (near crows) • Fewer cats per unit effort

Question: Are the cats that are removed via spotlighting the same cats that are ranging into the jungle, threatening adult crows? GIS Data Layers Attributes Table After Using “Near” Tool Summary Table of Distance to Spotlighting Road Feral Cat Home Range

When area is 92.2 ha (922,000 square meters), radius = 541.74 meters Spotlighting Roads with Buffer Crow Nest Areas Within the Buffer Conclusions

 Crows often nest close to spotlighting roads

• Crow nest areas averaged 297 meters (+/- 208 SD; range: 21-1052) from spotlighting roads

 Spotlight hunting is likely to be an effective method of removing cats from crow nest areas

• 87% of crow nest areas (40 of 46) fell within the 541 meter buffer Limitations of Current Study and Suggestions for Future Research

 Home range size used for cats was extremely conservative

• No data available for cat home range size on Rota

 Topography of Rota (e.g. cliffs) were not considered  How do cats move in cliffy landscape?

 Points were used for nest areas of Mariana Crows; crow home range was not incorporated

• Mariana Crow home range size data is available and could be used in future spatial analyses Questions?