Habitat fragmentation provides a competitive advantage to an invasive tree squirrel, Sciurus carolinensis

Jessen, Tyler; Wang, Yiwei; Wilmers, Christopher C.

doi:10.1007/s10530-017-1560-8

Cited by 17 publications

(14 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the goal of conservation is often to reverse declines of sensitive species rather than maximize species richness. Fragmentation and changes in the matrix frequently attract generalist or edge-adapted species that would otherwise be absent from landscapes comprising mostly core habitat (e.g., Jessen, Wang, & Wilmers, 2017;Major et al, 2001;Wethered & Lawes, 2003). Using species richness to measure ecosystem intactness means that local extinction of sensitive species is obscured by colonization by common species (Haddad et al, 2016).…”

Section: Dementioning

confidence: 99%

The importance of core habitat for a threatened species in changing landscapes

Herse

With

Boyle

2018

Journal of Applied Ecology

View full text Add to dashboard Cite

Habitat loss, fragmentation, and alteration of the landscape matrix are interdependent processes, collectively responsible for most recent species extinctions. Thus, determining the extent to which these landscape processes affect animals is critical for conservation. However, researchers have often assumed that interdependent effects are independently related to animals’ responses, underestimating the importance of one or several landscape processes in driving species declines. We demonstrate how to disentangle the interdependent effects of habitat amount, fragmentation, and edge context on population size by assessing abundance of a rapidly declining grassland songbird species (grasshopper sparrow Ammodramus savannarum) in eastern Kansas (USA). We conducted >7,000 point count surveys at >2,000 sites over two breeding seasons, then modelled the direct, interactive, and indirect effects of landscape factors on abundance within spatial scales (200‐, 400‐, 800‐, and 1,600‐m radii) relevant to our focal species’ dispersal behaviour. Sparrow abundance correlated most strongly with landscape structure within 400‐m radii, increasing nonlinearly with grassland area and decreasing with the proportion of grassland near cropland or woody edges. Sparrows’ negative response to cropland edges was mostly an added, indirect consequence of reduced grassland area, whereas sparrows’ stronger negative response to woody edges was not attributable to variation in grassland area. Fragmentation and edge context mattered most in landscapes comprising c. 50%–80% grassland. Synthesis and applications. In our research, abundance of a threatened grassland songbird was influenced more by core grassland area (a function of total grassland area, fragmentation, and edge context) than total grassland area per se. Moreover, a local extinction threshold of c. 50% grassland indicated that small amounts of habitat were unsuitable for our focal species regardless of habitat configuration or matrix type. Local extinction thresholds in response to habitat area provide clear baseline targets for land managers; above those thresholds, configuration and the matrix can be modified to increase abundance of edge‐sensitive animals. Conflicting evidence in the literature regarding the importance of fragmentation and matrix features could be partially explained by species‐level traits, or methodological issues such as defining landscapes at ecologically arbitrary spatial scales, assessing landscape quality using species richness, and ignoring interactive and indirect effects.

show abstract

Section: Dementioning

confidence: 99%

The importance of core habitat for a threatened species in changing landscapes

Herse

With

Boyle

2018

Journal of Applied Ecology

View full text Add to dashboard Cite

show abstract

“…Eastern gray squirrels (Sciurus carolinensis) thrive in urban environments (Jessen et al, 2018), expand populations throughout native environments in the United States (Koprowski et al, 2016) and show high success rates of establishment and invasion (80% success rate or 59 out of 74 introductions, see Bertolino, 2009) in non-native environments such as the United Kingdom, Ireland, Italy, and South Africa (Gonzales, 2005). Because the gray squirrel is considered one of the top one-hundred invasive species in the world (Lowe et al, 2004), EU law (see EU Regulation 1143/2014 on Invasive Alien Species) prohibits translocations to another country and thus, prevents a much preferable common garden approach for our investigation.…”

Section: Introductionmentioning

confidence: 99%

Cognitive Performance of Wild Eastern Gray Squirrels (Sciurus carolinensis) in Rural and Urban, Native, and Non-native Environments

2021

View full text Add to dashboard Cite

Enhanced cognitive ability has been shown to impart fitness advantages to some species by facilitating establishment in new environments. However, the cause of such enhancement remains enigmatic. Enhanced cognitive ability may be an adaptation occurring during the establishment process in response to new environments or, alternatively, such ‘enhancement’ may merely reflect a species’ characteristic. Based on previous findings that have shown ‘enhanced’ cognitive ability (i.e., higher success rate in solving novel food-extraction problems or, ‘innovation’) in Eastern gray squirrels (Sciurus carolinensis), a successful mammalian invader and urban dweller, we used an intraspecific comparative paradigm to examine the cause of their ‘enhanced’ cognitive ability. We conducted a field study to compare cognitive performance of free-ranging squirrels residing in rural and urban habitats in native (United States) and non-native environments (United Kingdom). By using established tasks, we examined squirrels’ performance in easy and difficult, novel food-extraction problems (innovation), a motor memory recall test of the difficult problem, and a spatial learning task. We found that the four groups of squirrels showed comparable performance in most measures. However, we also found that the native urban squirrels showed: (1) higher success rate on the first visit for the difficult problem than the non-native urban squirrels; (2) some evidence for higher recall latency for the difficult problem after an extended period than the non-native rural squirrels; and (3) learning when encountering the same difficult problem. These results suggest that the previously reported ‘enhanced’ performance is likely to be a general characteristic and thus, a pre-adaptive phenotypic trait that brings fitness advantages to this species in a new environment. Despite this, some cognitive abilities in gray squirrels such as solving novel problems has undergone mild variation during the adaptive process in new environments.

show abstract

“…Mammals vary in their sensitivity to fragmentation and in their adaptive responses to fragmentation (Crooks, 2002;Janecka et al, 2016;Palmeirim et al, 2020;Smith et al, 2019). For example, a disturbance from fragmentation may shuffle species distributions and facilitate the invasion of non-native competitors or other species (Crooks, 2002;Echeverría et al, 2007;Jessen et al, 2018). Overall, the impacts of fragmentation are even less clear for mesocarnivores, many of which are generalists and have smaller home ranges than their larger counterparts, and thus may be more resistant to or even benefit from fragmentation (but see Crooks et al, 2017;Rocha et al, 2020).…”

Section: Introductionmentioning

confidence: 99%