Rutting and rambling: Movement characteristics reveal partial migration in adult male white-tailed deer at a latitude void of chronic and severe environmental fluctuations

Abstract

White-tailed deer (Odocoileus virginianus) are generally considered a home-ranging species, although northern populations may migrate between summer and winter ranges to balance resource requirements with environmental stressors. We evaluated annual home range characteristics of adult bucks (n = 30) fitted with GPS collars from 2017 to 2021 in central Mississippi with time series segmentation and Kernel Density Estimation (KDE) to determine if individuals employed varying movement strategies. We found 67% of bucks displayed a "sedentary" strategy characterized by a single KDE home range polygon with a mean size of 361 ha. The remaining 33% of bucks employed a "mobile" strategy characterized by multiple home range segments with a mean size of 6530 ha. Sedentary bucks went on an average of 5.9 excursions annually while mobile bucks went on 0.8. Excursion timing for both strategies peaked in breeding season and early spring. Mobile buck home ranges were separated by a mean distance of 7.1 km and mean duration in one home range segment before traveling to another was 78 days. Our study provides the first evidence that partial migration may apply to a larger proportion of lower-latitude deer populations than originally thought, though the environmental justification for this partial migration is not clear.

Keywords: excursions; home range; migration; movement strategy; partial migration; white‐tailed deer.

FIGURE 1

Study area 1 (approximately 20,000 ha) along the Big Black River and study area 2 (approximately 15,000 ha) along the Mississippi River in central Mississippi, USA.

FIGURE 2

Example Net Squared Displacement plot from GPS locations. Lavielle segments are distinguished by vertical red lines at which a shift between home range segments occurs. For traditional Kernel Density Estimation (KDE) and Brownian Bridge Movement Models, all GPS data were used to estimate 50% and 95% utilization distributions (UD). In our segmented approach to KDE, all spatially overlapping segments labeled A were extracted, grouped, and used to create a UD. We applied the same process to segments labeled B, resulting in two home ranges for each individual.

FIGURE 3

Relocation cluster patterns and respective strategy classifications for GPS collared bucks. Sedentary bucks (a) have a single cluster of relocations and mobile bucks and (b) have spatially discrete clustering. Within the mobile strategy, shifts represent less‐frequent trips between home range segments after which a buck remains in the home range segment for an extended duration while bounces are rapid intra‐Lavielle segment trips back and forth to his other home range segment.

FIGURE 4

Buck #13 has a “sedentary” strategy characterized by relatively stable and non‐cyclic changes in NSD over time. Buck #13's GPS locations in this plot were taken during 2017–2018 in the Big Black River Region of Mississippi, USA.

FIGURE 5

Buck #297's year one data is an example of a “mobile” strategy characterized by dramatic and cyclic shifts in NSD over time. Lavielle segments are distinguished by vertical red lines. Buck #297's GPS locations in this plot were taken during 2017–2018 in the Big Black River Region of Mississippi, USA.

FIGURE 6

Buck #297's year two data contain “bouncing” behaviors, characterized by dramatic and cyclic shifts in NSD over time within Lavielle segments distinguished by vertical red lines. Bounces differ from excursions in that bounces are rapid trips back and forth between home range segments, whereas excursions are short‐duration trips to a location outside the home range boundary. Buck #297's GPS locations in this plot were taken during 2018–2019 in the Big Black River Region of Mississippi, USA.

FIGURE 7

Proportion of bounces between home range segments (n = 44 bounces) by month for GPS collared bucks during 2017–2021 in central Mississippi, USA.

FIGURE 8

Proportion of shifts between home ranges (n = 40 shifts) by month for GPS collared bucks with a mobile strategy during 2017–2021 in central Mississippi, USA.

FIGURE 9

Proportion of excursions (n = 189 excursions) by month for GPS collared bucks during 2017–2021 in central Mississippi, USA. Excursions are any GPS point(s) ≥0.5 km outside a buck's 95% KDE isopleth.