I'm Not Falling for That: Low Boldness and Trappability of Black Rats Impact Small Mammal Survey in Urban Reserves

Abstract

Small mammal diversity is crucial for maintaining the functioning of urban ecosystems. However, small mammal diversity estimates obtained by live-trapping are strongly influenced by animal behaviour. We live-trapped small mammals in five urban reserves, each paired with a natural forest counterpart within Ku-ring-gai Chase National Park, New South Wales, Australia. We used Elliot traps paired with camera traps to observe the activity, boldness, and trappability of small mammals. We found that the activity of small mammals did not differ between the urban reserve and forest sites. However, we found that the most active species in urban reserves was the invasive black rat (Rattus rattus; Muridae), whereas the native bushrat (R. fuscipes; Muridae) was the most active species in forest sites, which greatly influenced our results. We found that the small mammals in the urban reserves were less bold and had lower trappability than their forest counterparts. This could be explained by the bait type, and/or traits of the small mammal species (mostly R. rattus) that were dominant in the urban reserves. Our study also highlights the importance of using camera-trapping in conjunction with live-trapping when assessing small mammal behaviour towards trapping devices to increase the accuracy of diversity estimates obtained by live-trapping.