Bison movements change with weather: Implications for their continued conservation in the Anthropocene.

Animal movement patterns are affected by complex interactions between biotic and abiotic landscape conditions, and these patterns are being altered by weather variability associated with a changing climate. Some animals, like the American plains bison (Bison bison L.; hereafter, plains bison), are considered keystone species, thus their response to weather variability may alter ecosystem structure and biodiversity patterns. Many movement studies of plains bison and other ungulates have focused on point-pattern analyses (e.g., resource-selection) that have provided information about where these animals move, but information about when or why these animals move is limited. For example, information surrounding the influence of weather on plains bison movement in response to weather is limited but has important implications for their conservation in a changing climate. To explore how movement distance is affected by weather patterns and drought, we utilized 12-min GPS data from two of the largest plains bison herds in North America to model their response to weather and drought parameters using generalized additive mixed models. Distance moved was best predicted by air temperature, wind speed, and rainfall. However, air temperature best explained the variation in distance moved compared to any other single parameter we measured, predicting a 48% decrease in movement rates above 28°C. Moreover, severe drought (as indicated by 25-cm depth soil moisture) better predicted movement distance than moderate drought. The strong influence of weather and drought on plains bison movements observed in our study suggest that shifting climate and weather will likely affect plains bison movement patterns, further complicating conservation efforts for this wide-ranging keystone species. Moreover, changes in plains bison movement patterns may have cascading effects for grassland ecosystem structure, function, and biodiversity. Plains bison and grassland conservation efforts need to be proactive and adaptive when considering the implications of a changing climate on bison movement patterns.

Role of the thermal environment in scaled quail (Callipepla squamata) nest site selection and survival.

Temperature is increasingly recognized as an important component of wildlife habitat. Temperature is particularly important for avian nest sites, where extreme temperatures can influence adult behavior, embryonic development, and survival. For species inhabiting arid and semiarid climates, such as the scaled quail (Callipepla squamata), frequent exposure to extreme temperatures may increase the importance of the nest microclimate. Limited data suggest that scaled quail respond to temperature when selecting nest sites, and they are also known to respond to the presence of surface water and shrub cover on the landscape, two resources which may mitigate thermal stress. To better understand the role of temperature in nest site selection and survival, and to evaluate how other landscape resources may benefit nesting quail, we investigated nest site characteristics of scaled quail in southeastern New Mexico, USA. During the breeding seasons of 2018 and 2019 we located nests, monitored nest fate, and recorded thermal and vegetation characteristics at three spatial scales: the nest bowl, the nest microsite (area within 10 m of the nest bowl), and the landscape. We found that nest bowls moderated temperature relative to both the surrounding microsite and the broader landscape, remaining almost 5 °C cooler on average than the surrounding microsite at mid-day. Nest bowls also had taller, greater cover of vegetation compared to both the surrounding microsites and the landscape. Despite apparent selection for cooler temperatures and taller vegetation, these characteristics demonstrated a weak relationship with nest survival. Rather, nest survival was positively influenced by proximity to surface water and honey mesquite (Prosopis glandulosa), with survival decreasing with increasing distance from these features. Although the mechanism for this relationship is unclear, our results support the importance of temperature for nest site selection of ground-nesting birds in semiarid landscapes, and suggest further exploration of landscape-level sources of thermal mitigation.

Perspectives on grassland conservation efforts: should we rewild to the past or conserve for the future?

Grasslands are among the most imperilled biomes of the world. Identifying the most appropriate framework for restoring grasslands is dependent on the objectives of restoration, which is inherently determined by human priorities. Debates over the appropriate conservation model for grasslands have often focused on which species of herbivores should be the focus of restoration efforts. Here we discuss three perspectives of herbivore-based conservation in North American grasslands. First, the Pleistocene rewilding perspective is based upon the idea that early humans contributed to the demise of megafauna that were important to the evolution and development of many of North America's grasslands; therefore, their aim of restoration is rewilding of landscapes to pre-human times. Second, the bison rewilding perspective considers American bison a keystone herbivore that is culturally and ecologically important to North American grasslands. A third perspective focuses on restoring the pattern and processes of herbivory on grasslands and is less concerned about which herbivore is introduced to the landscape. We evaluate each of these three conservation perspectives in terms of a framework that includes a human domain, an herbivore domain and a biophysical domain. While all conservation perspectives partly address the three domains, they all fall short in key areas. Specifically, they fail to recognize that past, current and future humans are intimately linked to grassland patterns and processes and will continue to play a role in structuring grasslands. Furthermore, these perspectives seem to only superficially consider the role of fragmentation and climate change in influencing grassland patterns and processes. As such, we argue that future grassland conservation efforts must depend on the development of a model that better integrates societal, economic and policy objectives and recognizes climate change, fragmentation and humans as an integral part of these ecosystems.This article is part of the theme issue 'Trophic rewilding: consequences for ecosystems under global change'.