Spatial structure of reproductive success infers mechanisms of ungulate invasion in Nearctic boreal landscapes

1. Landscape change is a key driver of biodiversity declines due to
habitat loss and fragmentation, but spatially shifting resources can also
facilitate range expansion and invasion. Invasive populations are
reproductively successful, and landscape change may buoy this success. 2.
We show how modelling the spatial structure of reproductive success can
elucidate the mechanisms of range shifts and sustained invasions for
mammalian species with attendant young. We use an example of white-tailed
deer (deer; Odocoileus virginianus) expansion in the Nearctic boreal
forest, a North American phenomenon implicated in severe declines of
threatened woodland caribou (Rangifer tarandus). 3. We hypothesized that
deer reproductive success is linked to forage subsidies provided by
extensive landscape change via resource extraction. We measured deer
occurrence using data from 62 camera-traps in northern Alberta, Canada,
over three years. We weighed support for multiple competing hypotheses
about deer reproductive success using multi-state occupancy models and
generalized linear models in an AIC-based model selection framework. 4.
Spatial patterns of reproductive success were best explained by features
associated with petroleum exploration and extraction, which offer early
seral vegetation resource subsidies. Effect sizes of anthropogenic
features eclipsed natural heterogeneity by two orders of magnitude. We
conclude that anthropogenic early seral forage subsidies support high
springtime reproductive success, mitigating or exceeding winter losses,
maintaining populations. 5. Synthesis and Applications. Modelling spatial
structuring in reproductive success can become a key goal of remote
camera-based global networks, yielding ecological insights into mechanisms
of invasion and range shifts to inform effective decision-making for
global biodiversity conservation.