OCCUPANCY OF BREEDING SIKA DEER POPULATIONS AND COMPETITION WITH WHITE-TAILE DEER ON THE DELMARVA PENINSULA, USA
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Abstract
Sika deer were introduced to the Delmarva Peninsula in 1916 and have
become an important game species, cultural icon, and agricultural pest. Although sika
deer bring many economic benefits to the Eastern Shore, their ongoing range
expansion, potential distribution, and impacts on native species are poorly understood.
My objectives were to 1) identify landscape characteristics that predict occupancy of
breeding sika deer populations in order to assess potential range across the Delmarva
Peninsula and 2) assess whether competition with sika deer impacts white-tailed deer.
I used trail cameras baited with 11kg of corn to survey 100 sites in Dorchester,
Wicomico, and Somerset counties in Maryland during the winters of 2022, 2023, and
2024. Sika deer occupancy probability increased with increasing forest or marsh cover
at the 161 ha scale (95% CI 0.015, 0.056). An index of sika deer abundance was
negatively associated with an index of abundance for white-tailed deer (95% CI: -
0.099, -0.039), white-tailed deer detection probability (95% CI: -0.096, -0.131), and
occupancy probability (95% CI: -0.57, -0.13). Sika deer will likely colonize southern
portion of the Delmarva Peninsula, characterized by extensive forest and marsh cover
and high connectivity. Highly suitable patches set within the agriculturally dominated
northern half of the peninsula may lack the connectivity required for sika colonization.
Sika deer likely cause declines in sympatric white-tailed deer populations but
agriculturally dominated landscapes may act as refugia for white-tailed deer and
population management may facilitate the coexistence of both species.