Article

Behavioral Responses of Eastern Gray Squirrels in Suburban Habitats Differing in Human Activity Levels

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

We observed the alert responses of Sciurus carolinensis (Eastern Gray Squirrel) to two different approach stimuli (human only and human with a leashed dog) in two suburban habitats differing in the level of human activity. Alert distance in the habitat with higher levels of human activity was significantly shorter than the alert distance in the habitat with lower levels of human activity. Overall, the alert distance did not differ between the approach by a human alone and the approach by a human with a dog; however, in the high human activity sites (but not the low human activity sites), the presence of the dog increased alert distance in the squirrels. In addition, squirrels tended to initially respond by running more in the high human activity sites, but the presence of the dog increased the number of squirrels whose initial responses were to not run. Our results suggest that Eastern Gray Squirrel antipredator behavior, at least in response to humans and human-associated animals, is influenced by the level of human activity in the surrounding habitat.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Animals routinely exposed to human presence may be less disturbed by them-allowing for closer approaches. Following this logic, researchers have found a consistent pattern of decreasing FID with increasing human exposure in multiple species of sciurids (Chapman et al. 2012, Cooper et al. 2008, Engelhardt and Weladji 2011, Uchida et al. 2016) as well as birds (Carrete andTella 2010, Ducatez et al. 2016). ...
... Sciurus carolinensis (Eastern Gray Squirrels, Gmelin, 1788) are a particularly good focal species for urban behavioral studies due to their synanthropic distribution and abundance in both urban and non-urban habitats. This species is successful in urban environments and is commonly habituated to human presence (Bateman and Fleming 2014, Cooper et al. 2008, Engelhardt and Weladji 2011. Previous behavioral studies have examined relationships between risk assessment behavior, such as FID, and a variety of ecological and environmental factors. ...
... Previous behavioral studies have examined relationships between risk assessment behavior, such as FID, and a variety of ecological and environmental factors. This body of research has established that squirrels flee at shorter distances (e.g., are less wary of human approach) in sites with higher levels of human activity (Cooper et al. 2008), greater squirrel density (Parker and Nilon 2012), and distance to refuge (Dill and Houtman 1989, but see Engelhardt and Weladji 2011). Furthermore, human behavior has also been correlated with altered FID, with squirrels fleing more readily when humans approach while looking directly at them (Bateman and Fleming 2014). ...
... Highly--mobile species that are generalists in both food and habitat preference seem to have the best chances of survival in human disturbed areas; they may even benefit from the artificial food sources that human--populated areas can provide (Bayne and Hobson 2000;Engelhardt and Weladji 2011). Living in areas populated by humans may lead to habituation, whereby the animal becomes desensitized to human presence by repeated exposure (Cooper et al. 2008;Engelhardt and Weladji 2011;McCleery 2009). Flight initiation distance, the distance at which a potential predator can approach an animal before it flees, can be used as a measure of habituation (Engelhardt and Weladji 2011;McCleery 2009). ...
... Optimal escape theory suggests that an animal's Squirrel Habituation in Human Disturbed Areas (Bjordal) University of Saskatchewan Undergraduate Research Journal 36 decision to flee is flexible, based on maximum fitness possible from remaining stationary versus fleeing (Cooper and Frederick 2007;Engelhardt and Weladji 2011). Squirrels are one of the many wildlife species that has had to adapt to living in human impacted areas (Bayne and Hobson 1998;Bayne and Hobson 2000;Cooper et al. 2008;Engelhardt and Weladji 2011;McCleery 2009). In central Saskatchewan, there are two species of squirrels: northern flying squirrels (Glaucomys sabrinus) and the North American red squirrel (Tamiasciurus hudsonicus) (Bayne and Hobson 1998). ...
... If squirrels regard humans as predators, this will affect their flight initiation distance when approached by a person (Cooper et al. 2008;Engelhardt and Weladji 2011). My hypothesis was that if squirrels can become habituated to humans, then squirrels in densely human--populated areas will have a shorter flight initiation distance when approached by a human than squirrels in less populated areas. ...
Article
Human population growth results in destruction of natural habitats, although some animals are adapting to living in areas with human disturbance. North American red squirrels (Tamiasciurus hudsonicus) may be one such species that is successfully adapting to living alongside humans. Flight initiation distance, the distance at which an animal flees from an approaching predator, may act as an indicator of habituation to humans. I predicted that if North American red squirrels were habituating to humans, their flight initiation distance would decrease along a gradient of increasing human disturbance. To examine this, I measured flight initiation distances of 39 North American red squirrels across eight sites, classified as low, medium or high human disturbance areas. No significant difference was found in mean flight initiation distances between disturbance levels, indicating that squirrel flight initiation distance may not be sensitive to small scales of human disturbance gradients.
... Eastern grey squirrels Sciurus carolinensis are extremely successful urban adapters, and can be found in high densities in urban parks where they face reduced predation and become habituated to human presence, to the point where they show minimal avoidance behaviour of people (Cooper et al., 2008;McCleery, 2009;Engelhardt & Weladji, 2011). Eastern grey squirrels also have a lower giving-up density (i.e. ...
... We examined the behaviour of a population of eastern grey squirrels in a highly urbanized area -the lower east side of Manhattan, New York. We predicted that squirrels would show highly reduced antipredator behaviour because of habituation to human presence (as demonstrated by Cooper et al., 2008, Engelhardt & Weladji, 2011, but should still discriminate between different levels of threat posed by people, and appropriately dynamically upgrade their antipredator response. We therefore tested two experimental treatments. ...
... Squirrels allow pedestrians to approach closely compared with conspecifics in rural areas (e.g. FID 10.4 ± 6.65 m; Cooper et al., 2008). PCVST squirrels are mostly exposed to pedestrians acting in a benign, predictable manner, but show different responses towards pedestrians showing more irregular behaviour, presumably because they perceive it as more risky. ...
Article
Full-text available
Optimal escape theory predicts that animals should moderate their flight responses according to the level of risk represented by a potential predator. This theory should apply even when organisms are habituated to disturbance, and how animals respond to human presence is likely to determine their success exploiting urban habitats. Therefore, urban animals should be sensitive to cues that inform them about levels of risk, allowing them to reduce costs by not overreacting to innocuous stimuli, while ensuring that they are nevertheless reactive to genuinely threatening stimuli. We tested this at a highly urbanized site in New York City, where eastern grey squirrels appear to pay little attention to humans. Squirrels were approached tangentially on a trajectory that took the observer within ∼2 m of them and we measured alert distance, flight initiation distance (FID), and distance fled for each focal individual. Squirrels showed little sign of being alerted to the pedestrian if he remained on the footpath and did not look at them (only 5% of individuals moved away), but 90% of squirrels moved away, with longer FID and flight distance, when approached by a pedestrian that moved off the footpaths and looked at them. Squirrels therefore modulate their reactions when pedestrians behave in a predictable manner (i.e. remaining on the footpaths) and are also sensitive to the direction of attention of humans, reducing unnecessary responses, and are thereby likely to be increasing their ability to persist in this urban environment. Previous studies have emphasized the behavioural plasticity of successful urban wildlife species. In this study, we emphasize the importance of disturbance monitoring by successful urban exploiters, allowing them to vary their behavioural responses according to the level of risk to which they are exposed.
... Gray squirrels are diurnal and easy to spot. Urban populations become habituated to human presence and show reduced flight initiation distances, which are used to measure perceived predation risk (Cooper et al. 2008;Bateman and Fleming 2014;Engel et al. 2020). These characteristics make gray squirrels an excellent model species to study human food waste consumption. ...
... Trash bins were fuller during periods of high human presence and human presence positively influenced how many squirrels went on and inside a bin. Urban squirrels experience a reduced predation pressure and are less wary of humans compared to squirrels from rural habitats (Cooper et al. 2008;Parker and Nilon 2008;Bateman and Fleming 2014;Engel et al. 2020). Decreased wariness may explain why a higher level of disturbance, via high human presence at trash bins, did not have a negative effect on trash bin usage. ...
Article
Urban habitats provide wildlife with predictable, easily accessible and abundant food sources in the form of human food waste. Urban eastern gray squirrels (Sciurus carolinensis) are commonly observed feeding in trash bins, but we lack data regarding the type, quantity and seasonal changes in food waste usage. We observed five trash bins on an urban university campus during four different observation periods. We recorded the time squirrels spent on and inside trash bins and type of retrieved food items. We also recorded ambient temperature, human presence and trash bin filling. Moreover, we determined changes in squirrel population density in a natural and three anthropogenic habitats during the same periods. Trash bins were fuller when human presence was higher. The higher human presence, the more squirrels went on and inside the bin, but there was no effect on number of retrieved food items. Trash bin usage by squirrels decreased when ambient temperature and bin filling increased. Most food items were retrieved during the coldest observation period, a period of high human presence, and the majority of retrieved food items were starchy foods (e.g., bread, French fries). The relationship between the number of squirrels observed along transects and a measure of urbanization, the normalized difference built-up index, was negative in periods with high ambient temperatures and positive in periods with low ambient temperatures, indicating winter may be less challenging in urban areas, likely facilitated by the availability of anthropogenic food sources, allowing a higher level of activity throughout winter. Supplementary information: The online version contains supplementary material available at 10.1007/s42991-022-00326-3.
... For example, squirrels' behaviour and nest group sizes may be influenced by wariness levels towards humans (Parker and Nilon 2008;Rodríguez-Prieto et al. 2009;Uchida et al. 2016). Land-use types, particularly with high human activities, may influence the antipredator behaviour by squirrels (Cooper et al. 2008;Engelhardt and Weladji 2011). Squirrels may select the host tree species based on food abundance (Krauze-Gryz et al. 2016;Reher et al. 2016) and nest site attributes, such as host tree height and nest status, such as active or abandoned nests (Ocaña-Mayorga et al. 2018). ...
... FID is generally defined as "the distance at which an animal moves away from an approaching threat" (Blumstein 2003). Thus, FID is a measure of antipredator behaviour that reflects the tolerance towards approaching threats, such as humans (Møller et al. 2013;Cooper and Blumstein 2015;Young et al. 2020), and employed in this study to understand the impact of human activity on bush squirel's behaviour. There are several applications of FID by wildlife managers. ...
Article
Full-text available
The responses of wildlife to environmental factors are of conservation importance. However, the absence of relevant information due to inadequate studies, and lack of understanding of the influences of environmental factors on wildlife, particularly in the Zambezian bioregion, remain a conservation concern. For instance, there is a shortage of knowledge on the relationship between fixed effects of environmental factors and behaviour as well as nest group sizes of Smith's bush squirrels, Paraxerus cepapi Smith, 1836. Our study examined the relationship between fixed effects of several environmental factors (i.e., with focus on ecological factors) and the behaviour as well as nest group sizes of the bush squirrels in and around Zambia's Chembe Bird Sanctuary (CBS). Flight initiation distances (FIDs) as an index of bush squirrel behaviour, and nest group sizes were simultaneously surveyed to understand the drivers of biological and population responses, respectively. The results revealed that higher tree height (m) and larger canopy coverage (%) could increase FIDs for bush squirrels. The nest group sizes of bush squirrels could also increase with canopy coverage (%) and presence of termite mounds. By focusing on the two different squirrels' responses, the results of this study highlight the most important environmental factors to consider in minimizing the impacts of human activities on bush squirrels, especially in conservation planning and management by taking into consideration the bush squirrels' natural history, habitat protection and safe distance between humans and bush squirrels.
... Their body language is also complex, and the position and activity of their arms, tails and ears are all significant (Bates, 2014). Individual squirrels may display particular character traits, demonstrating more or less aggression, curiosity or willingness to tolerate risk (Cooper, Neff, Poon & Smith, 2008). ...
... But the systems that link humans and squirrels within the urban environment are constantly changing, producing new kinds of relationships and interactions. At the micro level, the presence of students and other human beings on campus has a cumulative effect on squirrel behaviour, making them less likely to flee both people and dogs (Cooper et al., 2008). At the macro level, many students travel to and from campus using vehicles that produce greenhouse gases, contributing to wide-reaching environmental change that impacts the lives of local gray squirrels among many other living creatures. ...
... This assay is similar to the widely used flight initiation distance test, where an observer approaches an animal to determine the distance at which the animal starts to run away (Ydenberg and Dill 1986), but here the goal was to determine the degree of an individual sea lion's response to human approach. It is similar to the methods used in a previous study on Galápagos sea lions (DeRango et al. 2019) and in other species, such as eastern gray squirrels (Cooper et al. 2008). To conduct this approach assay, an observer stood 6 m away from the focal sea lion and then slowly walked (~1 m s −1 ) towards its head. ...
... The approach stopped, either when the sea lion began moving toward the observer, or when the observer came within 2 m of the sea lion -the Galápagos National Park's minimum required distance from wildlife. Finally, the observer rated the sea lion's reaction to their approach on a scale of 0-5, with scores of 4 and 5 representing aggressive reactions: 0: the sea lion's eyes were closed (possibly asleep) and the sea lion did not react 1: the sea lion's eyes were open and the sea lion did not react 2: the sea lion lifted/moved its head to look at the observer 3: the sea lion moved away from the observer 4: the sea lion vocalized (growl or bark) 5: the sea lion moved toward the observer This 0-5 scale is an adaptation of the scales used to measure behavioral responses to human approach in squirrels (Cooper et al. 2008), polar bears (Dyck and Baydack 2004) and sea lions (Orsini et al. 2006, DeRango et al. 2019. ...
Article
Full-text available
The endangered Galápagos sea lion lives among a rapidly growing human population, and conflicts between humans and sea lions are increasing. Protection of this fragile species requires a better understanding of how anthropogenic activity affects its health and survival. In this study, we engaged a group of local students in a community science project to conduct long-term observations of the effects of human disturbance on sea lion behavior. We compared three types of behavior – reaction to human approach, vocalizations and group size – across four different haul-out sites which varied in their levels of human disturbance. We found that sea lions respond less aggressively to humans on beaches that are more disturbed. This may be because sea lions acclimate to human disturbance or because sea lions with a low tolerance for humans avoid disturbed sites. We also found that aggressive vocalizations between sea lions increase as sea lion group size increases, though group size was not linked to human disturbance. We did not quantify stress levels, but aggressive behavior often indicates elevated stress levels, which are energetically costly and can impair immune function. Our results suggest that conservation efforts should focus on limiting human–sea lion interactions and increasing the number and quality of available haul-out sites.
... Their body language is also complex, and the position and activity of their arms, tails and ears are all significant (Bates, 2014). Individual squirrels may display particular character traits, demonstrating more or less aggression, curiosity or willingness to tolerate risk (Cooper, Neff, Poon & Smith, 2008). ...
... But the systems that link humans and squirrels within the urban environment are constantly changing, producing new kinds of relationships and interactions. At the micro level, the presence of students and other human beings on campus has a cumulative effect on squirrel behaviour, making them less likely to flee both people and dogs (Cooper et al., 2008). At the macro level, many students travel to and from campus using vehicles that produce greenhouse gases, contributing to wide-reaching environmental change that impacts the lives of local gray squirrels among many other living creatures. ...
... We presented playback recordings to free-ranging gray squirrels throughout parks and residential areas in Oberlin, Ohio, USA. Squirrels in these areas were generally habituated to the presence of humans, allowing us to conduct playback trials at close distances without unduly disturbing them [27,28]. Nonetheless, we avoided sampling squirrels in parts of the study site that were heavily trafficked by humans to avoid disturbance during trials [28]. ...
... Squirrels in these areas were generally habituated to the presence of humans, allowing us to conduct playback trials at close distances without unduly disturbing them [27,28]. Nonetheless, we avoided sampling squirrels in parts of the study site that were heavily trafficked by humans to avoid disturbance during trials [28]. To avoid habituation of squirrels to the playbacks and resampling of individual squirrels, focal individuals were separated by at least 164 m (roughly, the home range of adult male eastern gray squirrels in woodland habitats [29]), and we did not conduct playback trials more than once at any site to avoid resampling the same squirrel [27]. ...
Article
Full-text available
When multiple species are vulnerable to a common set of predators, it is advantageous for individuals to recognize information about the environment provided by other species. Eastern gray squirrels (Sciurus carolinensis) and other small mammals have been shown to exploit heterospecific alarm calls as indicators of danger. However, many species-especially birds-emit non-alarm auditory cues such as contact calls when perceived predator threat is low, and such public information may serve as cues of safety to eavesdroppers. We tested the hypothesis that eavesdropping gray squirrels respond to "bird chatter" (contact calls emitted by multiple individuals when not under threat of predation) as a measure of safety. We compared vigilance behavior of free-ranging squirrels in the presence of playbacks of bird chatter vs non-masking ambient background noise lacking chatter after priming them with a playback recording of a red-tailed hawk (Buteo jamaicensis) call. Squirrels responded to the hawk call playbacks by significantly increasing the proportion of time they spent engaged in vigilance behaviors and the number of times they looked up during otherwise non-vigilance behaviors, indicating that they perceived elevated predation threat prior to the playbacks of chatter or ambient noise. Following the hawk playback, squirrels exposed to the chatter treatment engaged in significantly lower levels of vigilance behavior (i.e., standing, freezing, fleeing, looking up) and the decay in vigilance behaviors was more rapid than in squirrels exposed to the ambient noise treatment, suggesting squirrels use information contained in bird chatter as a cue of safety. These findings suggest that eastern gray squirrels eavesdrop on non-alarm auditory cues as indicators of safety and adjust their vigilance level in accordance with the vigilance level of other species that share the same predators.
... Although no prior studies have focused specifically on Abert's squirrel or dusky grouse, some research has investigated the effects of recreation on similar species. For example, responses of tree squirrels to recreation disturbance are typically greater in rural than in urban areas (Engelhardt & Weladji 2011) and may increase when humans are accompanied by domestic dogs (Cooper et al. 2008). Among grouse species, probability of occurrence and detections are significantly reduced near park entrances and hiking trails (Immitzer et al. 2014, Moss et al. 2014, and capercaillie (Tetrao urogallus) flush greater distances in areas with a higher intensity of recreation activity (Thiel et al. 2006). ...
... The only relationships we observed were weakly positive associations between detections of feeding sign and visitation levels by equestrians, cyclists, and all visitors (Table 5). Rather than indicating a positive effect of recreation activity on Abert's squirrels, we suspect these results indicate that Abert's squirrels are habituated to recreation activity, as has been demonstrated for other tree squirrel species (Cooper et al. 2008, Englehardt & Weladji 2011, and that the positive associations between feeding sign and visitation levels are attributable to an artefactual correlation with some unmeasured characteristic of the sampling locations that positively influenced both squirrels and recreational visitors. It is also possible there are other effects of recreation use on Abert's squirrels that we were not able to detect using feeding-sign surveys, such as changes in temporal activity patterns, physiological condition, or interactions with other species (e.g., pine squirrels [Tamiasciurus hudsonicus]). ...
Technical Report
Full-text available
Many protected land networks, including Boulder County Parks and Open Space (BCPOS) and Boulder Open Space and Mountain Parks (OSMP), operate under a dual mandate to provide public access for outdoor recreation while also protecting natural resources. However, there is growing evidence that recreation activity can negatively affect wildlife communities, and land and wildlife managers are seeking solutions to balance the benefits of outdoor recreation for human communities with its impacts on species and ecosystems. We conducted a pilot study of the potential effects of recreation on Abert's squirrel (Sciurus aberti) and dusky grouse (Dendragapus obscurus). The objectives of the study were to: (1) Test the effectiveness of survey methods for the target species; and (2) Examine relationships between the types and intensity of recreation use and target species detections. We selected 24 sampling locations in a factorial design among permitted activities (mountain biking and hiking, or hiking only), domestic dog policy (off-leash, on-leash, or excluded), and variation in recreation use intensity. We surveyed for Abert's squirrels using feeding-sign surveys, we surveyed for dusky grouse using dropping counts and acoustic monitoring, and we monitored recreation activity using remotely-triggered cameras. Detections of Abert's squirrels were positively associated with the density of large trees and negatively associated with the density of Douglas fir (Pseudotsuga menziesii). We did not find evidence for an effect of permitted activities, domestic dog policy, or recreation use intensity on Abert's squirrels. However, dusky grouse were detected less frequently in recreation areas where mountain bikes are permitted and in areas with greater visitation levels by cyclists, and we were unable to identify another characteristic of the sampling locations (e.g., vegetation characteristics) that could explain these relationships. Thus, we recommend that BCPOS and OSMP continue to monitor the potential effects of recreation on dusky grouse in future years. To do so, we recommend altering the research design to focus on sampling locations with habitat characteristics associated with dusky grouse (e.g., mixed conifer forests), switch from a plot-based to a point-transect survey design, employ acoustic monitoring as a primary survey method, and increase the total number of sampling locations. We also recommend that dusky grouse surveys be paired with community-level surveys for other species groups (e.g., point counts for passerine birds) to identify additional species that may be sensitive to recreation disturbance, and to account for possible interactions among species. Results of this research would help to balance the recreation and conservation goals of protected lands by informing ongoing management of recreation and supporting decisions regarding designated use of new acquisitions.
... Abundance and habitat use in the urban environment Urban animals face an environment that differs dramatically from natural settings, including increased fragmentation, roads, traffic, noise, human activity, altered distribution of food resources, and density and distribution of conspecifics (Cooper et al. 2008;Evans 2010;Partan et al. 2010;Sol et al. 2013). Some species are better able to tolerate urbanisation, and in these species density is often observed to increase dramatically compared to populations in more natural areas, one component of a phenomenon known as the "urban wildlife syndrome" (Parker & Nilon 2008). ...
... In urban greys, several behavioural changes related to vigilance, aggression, and communication have been noted. Intra-specific aggression generally increases as a function of increasing population density (Parker & Nilon 2008), and in urban areas specifically, grey squirrel wariness decreases as a function of increased human activity (Cooper et al. 2008). Grey squirrels communicate vocally and nonvocally by tail flicking and flagging in urban and rural environments, and the intensity of these vigilance behaviours in response to a robotic conspecific model increased in urban areas. ...
Chapter
Full-text available
Grey squirrels (Sciurus carolinensis) are common inhabitants of wooded urban and suburban parks throughout their native and introduced range. The ecology of grey squirrels in rural environments has been the focus of considerable research, yet the ecology, behaviours, economic impact, and conservation implications of urban grey squirrels continue to gain increasing attention. In this chapter, we summarise key ecological characteristics of grey squirrels (Sciurus carolinensis) within an urban/suburban environment and how these differ from those observed in rural environments, the ecological role grey squirrels play in an urban ecosystem, and associated management challenges. Whilst urban and rural grey squirrels select similar habitats, urban populations can occur at much higher densities than their rural counterparts, from which they exhibit behavioural differences. Urban grey squirrels provide a wide range of ecosystem services, including cultural services that result in many urban dwellers having positive attitudes towards grey squirrels. This presents challenges for managing conflicts that can arise due to the damage that grey squirrels can cause to infrastructure, vegetation and other wildlife. Understanding basic ecology and population dynamics of urban grey squirrels, particularly in their introduced range, is essential for predicting their risk of invasion and spread, impacts on native wildlife, and for designing control programmes.
... Habitat mediates the responses of some birds, perhaps because some habitats are impenetrable to dogs ( Mallord et al., 2007 ;Robinson and Pollitt, 2002 ). In forests, the American robin ( Turdus migratorius ) responded similarly to walkers the presence of a dog with a hiker elicited greater alert distances from eastern gray squirrels in areas with high human activity, interestingly, there was no corresponding effect in areas of low human activity, where alert distances were much greater for both types of stimuli ( Cooper et al., 2008 ), suggesting that wild mammals may have an easier time habituating to humans when they are common, but dogs will always be perceived as dangerous regardless of their ubiquity. ...
... Identical results were found for moufl on ( O. musimon ; Martinetto and Cugnasse, 2001 ) and mule deer also had a greater probability of fl eeing and a greater FID in response to hikers with a 'degree of response' refers to the level of behavioral response in a typical hierarchy of responses that escalate with increasing risk). Eastern gray squirrels ( Sciurus carolinensis ), in the presence of a dog compared to a human alone, tended to run less often and were more likely to freeze, erect, or fl ick their tails ( Cooper et al., 2008 ). In addition to these immediate reactions to the presence of dogs, some species may increase their group size to gain protection. ...
... The University of Maine campus, and other more urban areas, provide unique habitats where squirrels are somewhat protected from their natural predators, especially aerial predators like hawks. It was noticed that their predator response tactics are modified in areas with high human traffic, only fleeing when humans approached at shorter distances, while squirrels in low human activity areas fled when humans approached at longer distances (Cooper 2008). Since humans are less likely to hunt squirrels on the university campus than other natural predators, squirrels seem to let their guard down and are more often found scavenging for food, even those more unnatural food types like sunflower seeds. ...
... Eastern gray squirrels are also observed to have adapted to more urban areas that often have less tree cover than a forest undisturbed by humans (Cooper 2008). This is supported by a study conducted in St. Louis County, MO which observed an increase in eastern gray squirrel population with increases in food supply by bird feeders in urban and suburban areas where ornamental trees were being planted (Sexton 1990 With eastern gray squirrels' abilities to continue to recognize the energetic profitability of certain foods, even in an urban setting with little tree cover, along with a growing territory with favorable hardwood trees, they can easily and quickly intrude and take over red and fox squirrel habitat. ...
Article
The goal of this study was to observe the foraging behavior of Eastern Gray Squirrels (Sciurus carolinensis) on the University of Maine campus. The study tested whether squirrels in a more urban setting followed the optimal foraging theory, or if rarity of a food type played a greater factor in food selection. The study also examined whether urban squirrel behavior mimicked that of wild squirrels when presented with a food type uncommon on campus, but common in other parts of Maine, specifically the acorns of the white oak tree (Quercus alba). In three different areas on the campus, squirrels were given a number of different food types: English walnuts (Juglans regia), Spanish peanuts (Arachis hypogaea), red oak acorns (Quercus rubra), white oak acorns, and sunflower seeds (Helianthus annuus). Data were collected on which food item was taken and if they chose to eat or cache the item they had chosen. An overall pattern of the order in which the squirrels took the food was then established. Nutritional content was then taken into consideration to see if the squirrels followed the optimal foraging theory and if their behavior correlated with wild squirrels. A chi-square test confirmed the significance of their behavior. It was found that in the face of novel food types, squirrels do indeed follow the optimal foraging theory, and are able to estimate the profitability of food items. They do indeed follow the natural behaviors of eastern gray squirrels found in less urban settings.
... Habitat mediates the responses of some birds, perhaps because some habitats are impenetrable to dogs ( Mallord et al., 2007 ;Robinson and Pollitt, 2002 ). In forests, the American robin ( Turdus migratorius ) responded similarly to walkers the presence of a dog with a hiker elicited greater alert distances from eastern gray squirrels in areas with high human activity, interestingly, there was no corresponding effect in areas of low human activity, where alert distances were much greater for both types of stimuli ( Cooper et al., 2008 ), suggesting that wild mammals may have an easier time habituating to humans when they are common, but dogs will always be perceived as dangerous regardless of their ubiquity. ...
... Identical results were found for moufl on ( O. musimon ; Martinetto and Cugnasse, 2001 ) and mule deer also had a greater probability of fl eeing and a greater FID in response to hikers with a 'degree of response' refers to the level of behavioral response in a typical hierarchy of responses that escalate with increasing risk). Eastern gray squirrels ( Sciurus carolinensis ), in the presence of a dog compared to a human alone, tended to run less often and were more likely to freeze, erect, or fl ick their tails ( Cooper et al., 2008 ). In addition to these immediate reactions to the presence of dogs, some species may increase their group size to gain protection. ...
Article
This chapter studies the role of dogs as agents of disturbance in the wildlife, which causes disruption of normal activities and states of other species. It acknowledges the need for information regarding the disturbance caused by unaccompanied dogs. It also considers the possible factors that influence the wildlife disturbance by dogs.
... Animals exposed to high human contact may either increase their vigilance or flight responses (sensitisation), or may become habituated to human activity and show reduced responses, according to the nature of encounters with humans. Risky or dangerous encounters (e.g., with hunters, Stankowich, 2008; or when people have dogs with them, Mainini et al., 1993;Miller et al., 2001;Cooper et al., 2008) may elicit increased vigilance, while benign encounters with people (e.g., Cooper et al., 2008;Price, 2008;Rodriguez-Prieto et al., 2009) are likely to result in animals becoming habituated to human presence. Sensitisation/habituation may also be influenced by the behavioural plasticity of the species involved; for example, some taxa are better urbanadapters than others, and are better able to cope with exposure to humans (e.g., see Bateman & Fleming, 2012;Lowry et al., 2013). ...
... Animals exposed to high human contact may either increase their vigilance or flight responses (sensitisation), or may become habituated to human activity and show reduced responses, according to the nature of encounters with humans. Risky or dangerous encounters (e.g., with hunters, Stankowich, 2008; or when people have dogs with them, Mainini et al., 1993;Miller et al., 2001;Cooper et al., 2008) may elicit increased vigilance, while benign encounters with people (e.g., Cooper et al., 2008;Price, 2008;Rodriguez-Prieto et al., 2009) are likely to result in animals becoming habituated to human presence. Sensitisation/habituation may also be influenced by the behavioural plasticity of the species involved; for example, some taxa are better urbanadapters than others, and are better able to cope with exposure to humans (e.g., see Bateman & Fleming, 2012;Lowry et al., 2013). ...
Article
Full-text available
Species that are either sessile or too slow to resort to flight may instead rely on defences such as natural armour or protective structures, but they will still face the same economic decisions as do more mobile species about when to re-emerge from cover. The gopher tortoise (Gopherus polyphemus) is a species of conservation significance due to its important role as an ecosystem engineer and habitat loss due to human activities. In this study, we examined escape responses of gopher tortoises approached by a human observer. Our data supported our prediction that the level of disturbance would influence escape responses, with animals that were picked and handled taking longer to emerge and move off than animals that had simply been approached or approached and walked around. We also found that tortoises took half as long to extend their heads at our study site, where tortoises exposed to a high level of benign human activity over a long period, compared with an adjacent site where there had been minimal human interaction with tortoises. These data suggest that gopher tortoises adjust their escape responses according to the level of risk they are exposed to. Over the long-term, this plasticity in escape responses can potentially result in some level of habituation to human presence.
... Moreover, predation pressure is often altered in urban habitats and urban predators broaden their diet via inclusion of anthropogenic food sources (Eötvös et al. 2018, Gámez et al. 2022, Rodewald et al. 2011. Predation pressure on urban tree squirrels tends to be relaxed (Bowers andBreland 1996, McCleery et al. 2008), and urban squirrels are less wary of humans compared to squirrels from rural habitats (Bateman and Fleming 2014, Cooper et al. 2008, Engel et al. 2020, Parker and Nilon 2008. Access to abundant natural and anthropogenic food sources, together with an altered predation pressure, may explain why squirrels had lower HCC in the two most urbanized habitats included in this study. ...
Article
Wild animals face novel environmental challenges as natural habitats give way to urban areas, with numerous biotic and abiotic differences between the two. Urban ‘stressors’ may elicit a constant release of glucocorticoids via the hypothalamic–pituitary–adrenal (HPA) axis, and chronically elevated glucocorticoid levels can be associated with negative effects on health and reproduction. Reduced glucocorticoid secretion is proposed to facilitate adaptation to urban habitats by avoiding the negative health and reproductive effects of chronically elevated levels of circulating glucocorticoids. Here, we investigated this mechanism of adaptation to urban stress in a common species that occurs across the urban-rural gradient, and over a wide geographic range, Sciurus carolinensis (Eastern Gray Squirrel). We measured hair cortisol concentration (HCC), a long-term indicator of circulating glucocorticoids, of 192 squirrels from urbanized habitats and natural forest habitats in two study areas ~850 km apart, in the USA (N = 96 samples) and Canada (N = 96 samples). We examined the relationship between HCC and two correlated indices of urbanization, one reflecting vegetation (NDVI) and one reflecting human-made urban cover (NDBI). In the Canadian dataset, HCC showed quadratic relationships with NDVI and NDBI, indicating that squirrels have lower HCC in the most urbanized habitats (two university campuses). Males and females had similar HCC in the Canadian dataset. In the USA dataset, there was no relationship between HCC and either index, and males had higher HCC than females. These results suggest that urban habitats may be relatively benign for urban Eastern Gray Squirrels. Reduced glucocorticoid levels may represent a form of (phenotypic) plasticity that facilitates adaptation to and persistence in urban environments.
... Greater avoidance of humans by rodents-lagomorphs in areas that have higher coyote abundance and are closer to humandisturbed areas could be due to increased vigilance by the small mammals in these areas. A study on eastern gray squirrels (Sciurus carolinensis) found that they exhibited higher vigilance behaviors in areas of higher human activity compared with areas of lower human activity (Cooper et al., 2019). The time delays for bears after humans increased closer to tourist areas, trails, roads, and combined human-disturbance areas. ...
Article
Full-text available
Tourist activity in natural areas may impact species' behavior and ecology as well as predator-prey dynamics. Although previous research has demonstrated effects of human disturbance on wildlife communities, only a limited number of studies have focused on small mammals and coyote predator-prey systems. To generate an overview of human impacts on these wildlife communities, we analyzed camera trap data from a human-disturbed site at Lake Tahoe, California. To compare species' activity patterns in relation to distances from human-disturbed areas, we used single-species occupancy models, estimations of species' temporal activity overlaps, and the time between detections of different species at camera sites. We found that in general black bears (Ursus americanus) avoided areas of high human disturbance, whereas coyotes (Canis latrans), rodents, and lagomorphs favored them. However, rodents and lagomorphs also avoided areas with high coyote detections, indicating that rodents and lagomorphs mostly used human-disturbed areas that were not highly frequented by coyotes. Additionally, all aforementioned species avoided humans temporally and this avoidance increased in closer proximity to human-disturbed areas. These findings indicate that while some species frequented human-disturbed areas more than others, all species studied exhibited greater temporal avoidance of humans when closer to areas of higher human activity. Our results also indicate that rodents' and lagomorphs' activity patterns overlapped more with coyotes' activity patterns closer to human-disturbed areas and rodents and lagomorphs avoided coyotes less in these areas. The greater overlap of the species' activity patterns suggests that there is likely more interaction between coyotes and their prey closer to areas of high human activity. The changes in the behavior and ecology of wildlife communities closer to human-disturbed areas reported here emphasize how proximity to human-disturbed areas may influence both predator and prey demographics.
... This behavioural modification may be one of the adaptive responses in wild animals to urbanization. As predicted, we were able to approach urban red squirrels much closer than rural individuals, which are consistent with other studies on arboreal squirrels (Cooper et al., 2008;Mccleery, 2009). Squirrels are sometimes considered as an iconic species for 'happy coexistence' between humans and wildlife, since they are common in the parks of many metropolitan cities and appear adjusted to an urban lifestyle (Thorington et al., 2012). ...
... In our study sites, humans often walk their dogs in urban parks, and dogs usually do not approach squirrels either because of indifference or constrained by dog leashes. It is suggested that Eastern gray squirrels Sciurus carolnensis habituate also to dogs (Cooper et al. 2008). Because dogs and foxes are both medium-sized canids, habituation to domestic dogs might reduce the FID in response to the model fox (McCleery 2009). ...
Article
Full-text available
For resolving human-wildlife conflict, traditional wildlife management often uses population control. However, recent studies suggest that in some cases, there is a weak relationship between conflicts and population size. This is because some problem animals cause most of conflicts and other non-problem animals cause little conflicts. For resolving human-wildlife conflict, managing animal behavior could be effective. This study conducted hazing experiments for managing the sensitivity of wildlife (i.e., habituation and sensitization to humans), because sensitized wildlife should reduce conflicts. Behavioral studies predict this causal relationship, but little critical evaluation of the relationship has been tested in a wildlife management study. Therefore, practical and logical evaluation is needed. A hazing experiment and path analysis revealed that macaques which were frequently hazed using airsoft guns were sensitized and sensitized macaques had reduced conflicts with humans (i.e., crop damage and open land usage). In addition, using flight initiation distance, we developed simulation models which examined the effects of habituation and sensitization on conflicts. The simulation showed that a habituated population had increased conflicts and a sensitized population had reduced conflicts. These results supported the results of our hazing experiment. Both the field experiment and simulation showed the effectiveness of managing wildlife sensitivity practically and logically. Managing sensitivity could be another measure against human-wildlife conflicts. It should be noted that effective hazing did not need intense stimuli but did require high rate hazing.
... In our study sites, humans often walk their dogs in urban parks, and dogs usually do not approach squirrels either because of indifference or constrained by dog leashes. It is suggested that Eastern gray squirrels Sciurus carolnensis habituate also to dogs (Cooper et al. 2008). Because dogs and foxes are both medium-sized canids, habituation to domestic dogs might reduce the FID in response to the model fox (McCleery 2009). ...
Article
Full-text available
Increased boldness is one of the most prevalent behavioral modifications seen in urban animals and is thought to be a coping response to anthropogenic environmental alterations. Most previous studies have shown enhanced boldness manifested as changes in responses to humans approaching, such as reductions in flight initiation distance (FID). However, this includes two confounding factors related to “boldness,” that is, reduction of vigilance and habituation to humans. Confounding these totally different processes could lead to our misunderstanding of urban adaptation and how to properly manage urban wildlife. Here, we propose a simple framework to separate the two processes using two flight distance measures toward different approaching threats. We considered that the distance at which targeted individuals noticed an approaching object (i.e., alert distance, AD) was related to vigilance, whereas FID represented risk assessment, which is related to habituation. We applied a predictive framework using AD and FID to Eurasian red squirrels’ responses to multiple threats of different risk levels (i.e., humans, model predators, and novel objects). AD was shorter in urban individuals compared with rural ones but not different among the approaching objects. FID was shorter in urban individuals and also varied among the objects with the shortest FID toward humans, whereas rural individuals showed similar FID to the different objects. These results suggest that, although urban individuals showed reduced vigilance, they could still assess different risk levels. Our framework can easily be applied to many animals and could significantly improve our understanding of wild animals’ adaptations to urban environments.
... Mammals also had a relatively high rate of positive effects. Of the mammal Orders, rodents had the most evidence for positive effects; all but one of these effects were behavioral and most resulted from habituation (e.g., reduced flight responses in areas with higher levels of recreation; [78,79]. Habituation to recreation was discussed in many (39.4%) of the included articles and typically resulted in positive responses in our coding system (e.g., reduced flight initiation distances in habituated animals), but whether habituation is a beneficial outcome for animals (e.g., by reducing costly behavioral responses to humans) is unclear and warrants further study [80,81]. ...
Article
Full-text available
Outdoor recreation is typically assumed to be compatible with biodiversity conservation and is permitted in most protected areas worldwide. However, increasing numbers of studies are discovering negative effects of recreation on animals. We conducted a systematic review of the scientific literature and analyzed 274 articles on the effects of non-consumptive recreation on animals, across all geographic areas, taxonomic groups, and recreation activities. We quantified trends in publication rates and outlets, identified knowledge gaps, and assessed evidence for effects of recreation. Although publication rates are low and knowledge gaps remain, the evidence was clear with over 93% of reviewed articles documenting at least one effect of recreation on animals, the majority of which (59%) were classified as negative effects. Most articles focused on mammals (42% of articles) or birds (37%), locations in North America (37.7%) or Europe (26.6%), and individual-level responses (49%). Meanwhile, studies of amphibians, reptiles, and fish, locations in South America, Asia, and Africa, and responses at the population and community levels are lacking. Although responses are likely to be species-specific in many cases, some taxonomic groups (e.g., raptors, shorebirds, ungulates, and corals) had greater evidence for an effect of recreation. Counter to public perception, non-motorized activities had more evidence for a negative effect of recreation than motorized activities, with effects observed 1.2 times more frequently. Snow-based activities had more evidence for an effect than other types of recreation, with effects observed 1.3 times more frequently. Protecting biodiversity from potentially harmful effects of recreation is a primary concern for conservation planners and land managers who face increases in park visitation rates; accordingly, there is demand for science-based information to help solve these dilemmas.
... Eastern gray squirrels have also been noted to react differentially to predators, depending on the proximity of the predator and the associated risk [60][61][62][63]. Eastern gray squirrels that live in human-dense environments become accustomed to human proximity and do not react as strongly as their rural counterparts when approached [60,[63][64][65]. Furthermore, one constraint of existing in an urban environment is that eastern gray squirrels often rely at least partially on human refuse for food [45,65,66]. ...
Article
Full-text available
The eastern gray squirrel (Sciurus carolinensis) is known to gnaw on bone and thus has the potential to affect terrestrial surface remains in forensic scenes throughout its extensive geographic range in North America and other places in the world where it has been introduced. To determine the timing, extent, and characteristics of gnawing of this rodent species within an urban environment, an initial sample of 305 dry postcranial bones of white-tailed deer (Odocoileus virginianus) were wired to trees for a period of 8 weeks and observed every 2 weeks in multiple sites in Boston, Massachusetts. Squirrel gnawing damage included the typical parallel striations noted for rodents and the loss of epiphyses of long bones, marrow cavity exposure, and sculpting of bone margins, with a cumulative total of 58 out of the original sample of 305 bones (19.0%) having gnawing damage of some kind. When subtracting the bones lost during the experiment without previous gnawing, the cumulative total is 58 out of 271 bones (21.4%). Rodent gnawing can advance rapidly, potentially causing the loss of diagnostic bone features and obscuring previous trauma sites, and researchers should be aware of its effects on exposed skeletal remains.
... This behavioural modification may be one of the adaptive responses in wild animals to urbanization. As predicted, we were able to approach urban red squirrels much closer than rural individuals, which are consistent with other studies on arboreal squirrels (Cooper et al., 2008;Mccleery, 2009). Squirrels are sometimes considered as an iconic species for 'happy coexistence' between humans and wildlife, since they are common in the parks of many metropolitan cities and appear adjusted to an urban lifestyle (Thorington et al., 2012). ...
Article
Full-text available
Urbanization has caused significant behavioural modifications in wild animals. Change in anti-predator behaviour is the most widespread example across different taxa in urban areas, which is probably due to a decrease in predation pressure and habituation towards humans. Seasonality or phenology has also been modified by urbanization since some resources in urban environments are highly controlled, for example, artificial feeding. Under natural conditions, anti-predator responses vary with seasonal variability in environmental and individual conditions. However, resource stability possibly reduces the seasonality of anti-predator behaviours in urban animals. Here, we compare the seasonal difference of flight initiation distance (FID), a measurement of anti-predator response, in Eurasian red squirrels Sciurus vulgaris between urban and rural areas in the Tokachi region, Hokkaido, Japan. Rural squirrels possessed FIDs two to three times longer than those of urban squirrels. We also found squirrels in rural areas lowered FID in autumn, but no seasonal difference was observed in urban squirrels. Our results suggest that continuous supplementary feeding may have buffered the seasonality in anti-predator response. In addition, strong habituation to humans may allow urban red squirrels to correctly assess human activity as benign rather than reacting unnecessarily.
... Gray squirrels are well studied on other topics, however, including reproductive behavior (Koprowski, 1993(Koprowski, , 1996 and foraging (Makowska and Kramer, 2007;Steele et al., 2008). In terms of urban/rural comparisons, urban and rural gray squirrels have been studied in the context of resource acquisition (Bowers and Breland, 1996) and antipredator behavior (Cooper et al., 2008). Aggression and flight distance have also been studied in urban populations of gray squirrels (Gustafson and Van Druff, 1990;Parker and Nilon, 2008). ...
Article
Urbanization of animal habitats has the potential to affect the natural communication systems of any species able to survive in the changed environment. Urban animals such as squirrels use multiple signal channels to communicate, but it is unknown how urbanization has affected these behaviors. Multimodal communication, involving more than one sensory modality, can be studied by use of biomimetic mechanical animal models that are designed to simulate the multimodal signals and be presented to animal subjects in the field. In this way the responses to the various signal components can be compared and contrasted to determine whether the multimodal signal is made up of redundant or nonredundant components. In this study, we presented wild gray squirrels in relatively urban and relatively rural habitats in Western Massachusetts with a biomimetic squirrel model that produced tail flags and alarm barks in a variety of combinations. We found that the squirrels responded to each unimodal component on its own, the bark and tail flag, but they responded most to the complete multimodal signal, containing both the acoustic and the moving visual components, providing evidence that in this context the signal components are redundant and that their combination elicits multimodal enhancement. We expanded on the results of Parian et al. (2009) by providing data on signaling behavior in the presence and absence of conspecifics, suggesting that alarm signaling is more likely if conspecifics are present. We found that the squirrels were more active in the urban habitats and that they responded more to tail flagging in the urban habitats as compared to the rural ones, suggesting the interesting possibility of a multimodal shift from reliance on audio to visual signals in noisier more crowded urban habitats.
Article
Anthropogenic disturbances are widely recognized for their far-reaching consequences on the survival and reproduction of wildlife, but we understand comparatively little about their effects on the social lives of group-living animals. Here we examined these short-Term changes in affiliative behavior as part of a long-Term study on a human-Tolerant and socially flexible population of California ground squirrels (Otospermophilus beecheyi). We used social network analysis to examine short-Term changes in affiliative behavior and individual consistency in response to disturbances by humans, domestic dogs, or a natural predator (the coyote). Overall, juveniles were more involved than adults in affiliative interactions, but the short-Term directional effects of these acute disturbances on social cohesion varied by disturbance type. Human and dog presence reduced aboveground connectivity, particularly for juveniles, whereas disturbances by coyotes generally promoted it. Beyond these effects, we also detected non-random responses to disturbances, though individuals were not very consistent in their directional response to different disturbance types. Our results demonstrate the flexible changes in social behavior triggered by short-Term disturbances imposed by humans and other threats. More generally, our findings elucidate the underappreciated sensitivity of animal social interactions to short-Term ecological disturbances, raising key questions about their consequences on the social lives of animals. © 2022 The Author(s). Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.
Article
Animals in urban areas that experience frequent exposure to humans often behave differently than those in less urban areas, such as exhibiting less vigilance or anti-predator behavior. These behavioral shifts may be an adaptive response to urbanization, but it may be costly if animals in urban areas also exhibit reduced anti-predator behavior in the presence of natural predators. In trials with only a human observer as the stimulus, urban squirrels exhibited reduced vigilance and anti-predator behavior compared to those in less urban areas. Next, we exposed squirrels in multiple urban and less urban sites to acoustic playbacks of a control stimulus (non-predatory bird calls), a natural predator (hawk), and dogs and recorded their vigilance and three different anti-predator behaviors when a human approached them while either broadcasting one of these three playbacks or no playbacks at all. Squirrels at urban sites also did not differ in their behavioral responses to the playbacks from possible predators (hawks or dogs) when they were compared to those at less urban sites exposed to these playbacks. Urban squirrels also exhibited increased vigilance and anti-predator behavior when exposed to a human paired with hawk playbacks compared to the control playbacks. Together, our results indicate that urban squirrels did perceive and assess risk to the natural predator appropriately despite exhibiting increased tolerance to humans. These results provide little support for the hypothesis that increased tolerance to humans causes animals to lose their fear of natural predators.
Chapter
Habitat selection of a substrate or habitat to minimize predation implies a behavioral choice of the appropriate background. Use of a habitat may not imply a behavioral choice. Selection is a largely unexplored area, but it seems that some species select a background to rest in which it makes these animals less conspicuous to predators.
Chapter
As humans, we consistently judge the behavior of animals (e.g., that pet is cute) or fellow humans (e.g., that new neighbor is friendly, etc.) based on their appearance and how they act from our perspective. In other words, we seldom look at the ecology of a pet or human or, for that matter, of an animal in the wild. In contrast, wildlife managers typically look at the ecology of an animal or view the animal as being part of a population; management of a species is based on populations rather than on individuals; wildlife management classically focused on populations, habitat, and people (Giles 1978).
Article
In this fascinating book, Terry O’Connor explores a distinction that is deeply ingrained in much of the language that we use in zoology, human-animal studies, and archaeology-the difference between wild and domestic. For thousands of years, humans have categorized animals in simple terms, often according to the degree of control that we have over them, and have tended to see the long story of human-animal relations as one of increasing control and management for human benefit. And yet, around the world, species have adapted to our homes, our towns, and our artificial landscapes, finding ways to gain benefit from our activities and so becoming an important part of our everyday lives. These commensal animals remind us that other species are not passive elements in the world around us but intelligent and adaptable creatures. Animals as Neighbors shows how a blend of adaptation and opportunism has enabled many species to benefit from our often destructive footprint on the world. O’Connor investigates the history of this relationship, working back through archaeological records. By requiring us to take a multifaceted view of human-animal relations, commensal animals encourage a more nuanced understanding of those relations, both today and throughout the prehistory of our species.
Chapter
Storing food, becoming dormant, or migrating is one of three strategies that an animal may adopt to survive environmental harshness, e.g., winter cold and snow. The annual appearances and disappearances of birds were long a mystery (Gill 1990). For instance, Aristotle knew that cranes migrated from Asia to the Nile, but he believed that smaller birds hibernated. We now know that over 180 bird species migrate from Europe and Asia to Africa, and that over 170 species migrate from North America to the tropics each year.
Chapter
Wild animals in urban areas face unique challenges. They live in environments modified by and for humans without having evolved in these environments, but unlike domesticated animals, they remain under the auspices of natural selection. We do not yet know how living in urban areas will ultimately affect the animals that share our urban environments, but we are at the beginning of a new and important scientific effort to study the effects of urbanization on wildlife. Early signs suggest that animals that can tolerate urbanization are quite different in behavior and physiology than those that are limited in distribution to natural areas.
Article
Full-text available
Flight initiation distance (FID), the distance at which an organism begins to flee from an approaching predator or threat, is associated to prey escape decision-making processes with benefit and cost trade-offs to remaining in a patch. Factors that may affect FID can be altered by human-stimulated predation risk, although the magnitude of response may depend on human exposure. We investigated how FID and distance to refuge of foraging eastern gray squirrels (Sciurus carolinensis Gmelin, 1788), vary in seven sites corresponding to three levels of human exposure. We predicted that both FID and distance to refuge increase as exposure to human stimuli decreases; FID increases with the starting distance of the approaching human; and FID increases with distance to refuge. We found that FID increased with decreasing human exposure and that FID increased with increasing starting distance. We found no difference in distance to refuge between exposure levels. Our results suggest that risk posed to gray squirrels in areas frequently visited by humans is minimized or reduced, leading to differences in FID between exposure levels and may be attributed to habituation to increased nonlethal stimuli in the form of exposure to humans.
Article
Full-text available
Within the context of a study on tourist disturbance affecting Mediterranean Mouflon (Ovis gmelini musimon x Ovis sp.) in the Caroux-Espinouse massif (Hérault, France), we assessed the sensitivity of this species towards the presence of a dog (Canis familiaris) taken along by two hikers. With the help of standard experimental disturbance events we measured the distance at which Mouflons spotted a source of disturbance, modified their activity and became vigilant, as well as their escape distance. Three sources of disturbance were tested in the springs of 1996 to 1998 on the Caroux plateau, one of the areas in the massif with the highest tourist pressure: approach by two hikers, approach by two hikers with a leashed dog and approach by two hikers with a dog off leash. If the median Mouflon escape distance increases very significantly in the presence of a dog, the fact of keeping him on leash or allowing him to run does not make much difference: from 70 m (N = 95) when the two hikers are alone, the escape distance goes up to 100 m (N = 21) and 98.5 m (N = 36) when these persons are with a leashed or unleashed dog, respectively. Besides, the presence of two people with a dog may modify the behaviour of the Mouflons in an area of about 7.5 ha around them, whereas if the two people are alone under the same conditions, the disturbed area is only of about 3.7 ha. This increased sensitivity of Mouflons to the presence of a dog indicates a great stress, which is a long-term source of perturbation that could affect their population dynamics, like in the case of chases by dogs off leash (93.6% of cases). Therefore, and in the context of further development of ecotourism in the massif, the control of such disturbances must henceforth be envisaged.
Article
Full-text available
Melanism in the gray squirrel (Sciurus carolinensis) is currently found primarily in urban populations and near the northern limit of the species' range. Selected behaviors were examined in Syracuse, New York, to determine if significant differences exist between black and gray morphs which may have survival implications in urban environments and perhaps throughout the range of the gray squirrel. No differences in wariness between the morphs was demonstrated when flight response to approaching humans and dogs was tested. Although males were dominant over females and initiators of encounters usually were victors, neither color morph was more dominant in aggressive encounters at feeding stations. Quantification of sunning behavior during the months of February and March revealed no differences in behavioral thermoregulation between the two morphs. These results suggest that the distribution of color morphs is not due to pleiotropic behavioral trait differences, that neither morph is likely to have a mating advantage, and the variation among demes suggests random factors (drift).
Article
Full-text available
Although humans are commonly used as a surrogate predator to assess the antipredator behavior of lizards, little is known about the effects that life associated with humans may have on the escape behavior of lizards. Here we examine the effects that coexistence with humans may have on the antipredator mechanisms in three species of Liolaemus (Tropiduridae). For each species we compared two populations exposed to different human densities, to test the null hypothesis that there is no interpopulational variation in the response to an approaching human in the field. Also it was determined whether coexistence with humans would affect the behavioral and physiological antipredator responses to a model of a natural predator in the laboratory. Lizard populations that were exposed to a high human density allowed a closer proximity of humans in the field, and decreased their rate of movement and breathing intensity in response to the presentation of a predator model in laboratory experiments. We discuss the effects humans may have upon the lizards antipredator behavior toward humans and natural predators.
Article
Full-text available
Examined the effects of predation hazard on patch-residence time and meal size (usually taken as foraging decisions), as well as on travel time, handling time, and the gain function (usually taken as constraints on foraging decisions). Sciurus carolinensis were presented with 8 artificial patches of sunflower seeds of the same initial density (either 25, 50, 100 or 200) at one distance to cover (either 5 or 15 m). Squirrels ate the same quantity of seeds farther from cover, but they ate them significantly faster. Squirrels also travelled significantly faster between patches, and handled seeds significantly faster within patches when farther from cover. The change in the handling times caused the squirrels' gain functions to be higher farther from cover. -from Authors
Article
Full-text available
This study addressed behavioral responses by black-tailed prairie dogs (Cynomys ludovicianus) to human intrusion in urban and rural environments in Boulder, Colorado. We expected that if prairie dogs habituate to repeated disturbances, they should allow a recurring human intruder to approach closer over time before sounding an alarm bark or initiating concealment. We also predicted that urban colonies could be approached more closely than rural colonies before displaying an avoidance response. Four colonies (2 rural and 2 urban) were approached >100 times over a 7-month period. Rather than exhibiting habituation, prairie dogs demonstrated increased responsiveness in concealment behavior, retreating to their burrows earlier, with recurring disturbances. Barking distances did not change consistently with repeated intrusion, but, over time, prairie dogs barked less frequently when performing their avoidance response, a result with implications for prairie dog management. Rural colonies had higher initial concealment distances, and these distances increased more rapidly with repeated intrusion than did concealment distances in urban colonies. Thus, rural prairie dogs may be more sensitive to human intrusion than urban prairie dogs.
Article
Full-text available
Predation has long been implicated as a major selective force in the evolution of several morphological and behavioral characteristics of animals. The importance of predation during evolutionary time is clear, but growing evidence suggests that animals also have the ability to assess and behaviorally influence their risk of being preyed upon in ecological time (i.e., during their lifetime). We develop an abstraction of the predation process in which several components of predation risk are identified. A review of the literature indicates that an animal's ability to assess and behaviorally control one or more of these components strongly influences decision making in feeding animals, as well as in animals deciding when and how to escape predators, when and how to be social, or even, for fishes, when and how to breathe air. This review also reveals that such decision making reflects apparent trade-offs between the risk of predation and the benefits to be gained from engaging in a given activity. Despite this body of evidence, several areas in the study of animal behavior have received little or no attention from a predation perspective. We identify several such areas, the most important of which is that dealing with animal reproduction. Much work also remains regarding the precise nature of the risk of predation and how it is actually perceived by animals, and the extent to which they can behaviorally control their risk of predation. Mathematical models will likely play a major role in future work, and we suggest that modelers strive to consider the potential complexity in behavioral responses to predation risk. Overall, since virtually every animal is potential prey for others, research that seriously considers the influence of predation risk will provide significant insight into the nature of animal behavior.
Article
Full-text available
Human recreation has been implicated in the decline of several populations of desert bighorn sheep (Ovis canadensis nelsoni). Managers are concerned about the impact of increased recreation on desert bighorn sheep in Canyonlands National Park (NP), Utah, USA, where visitation increased 325% from 1979 to 1994. We compared behavioral responses of Sheep to recreational activity between a low visitor use area and a high visitor use area during 1993 and 1994 by observing behavioral responses, distances moved, and duration of responses to vehicles, mountain bikers, and humans on foot. Hikers caused the most severe responses in desert bighorn sheep (animals fled in 61% of encounters), followed by vehicles (17% fled) and mountain bikers (6% fled), apparently because hikers were more likely to be in unpredictable locations and often directly approached sheep. We observed considerable individual heterogeneity in responses of bighorn sheep to the greater human use: some animals lived close to the road corridor and were apparently habituated to the human activities, but other animals avoided the road corridor. In the high-use area, we observed 3 radiocollared sheep that lived closer to the road than expected and found evidence of fewer responses to vehicles by females in spring, less response time of all sheep to vehicles in spring, and fewer responses to mountain bikers compared to the low-use area. Overall, there was an avoidance of the road corridor by most other bighorn sheep in the high-use area where all animals, on average, were found 39% farther from roads (490 ± 19 m vs. 354 ± 36 m) than in the low-use area. This avoidance of the road corridor by some animals represented 15% less use of potential suitable habitat in the high-use area over the low-use area. Increased sensitivity to hikers in the high-use area was suggested by a greater responsiveness by males in autumn and greater distance fled by females in spring. Responses of bighorn sheep were greater when human activity approached at the same elevation, when sheep were moving or standing, when female interactions occurred in spring and summer and male interactions occurred in autumn, and when sheep were farther from escape terrain. We recommend managers confine hikers to designated trails during spring lambing and the autumn rut in desert bighorn sheep habitat.
Article
Full-text available
In the region of first near Grindelwald in the Swiss Alps, experiments were carried out on the reaction of alpine marmots Marmota marmota when confronted with hikers. Marmots in highly frequented areas showed less reaction to hiking activities than marmots in remote areas. In adult marmots, there was no change in reaction during the season. In young animals the reaction shortly after leaving the burrows in early July, was slight and similar in highly frequented and remote areas. In late summer, the intensity of the reaction of young animals increased significantly in animals in both study groups but to a much larger extent in the remote areas. We conclude that the perception of danger has to be learned or is built up during growth and development. At the same time, young animals in highly frequented areas may adjust to the presence of hikers.
Article
Full-text available
Outdoor recreation has the potential to disturb wildlife, resulting in energetic costs, impacts to animals' behavior and fitness, and avoidance of otherwise suitable habitat. Mountain biking is emerging as a popular form of outdoor recreation, yet virtually nothing is known about whether wildlife responds differently to mountain biking vs. more traditional forms of recreation, such as hiking. In addition, there is a lack of information on the ''area of influence'' (within which wildlife may be displaced from otherwise suitable habitat due to human activities) of different forms of recreation. We examined the responses of bison (Bison bison), mule deer (Odocoileus hemionus), and pronghorn antelope (Antilocapra americana) to hikers and mountain bikers at Antelope Island State Park, Utah, by comparing alert distance, flight distance, and distance moved. Within a species, wildlife did not respond differently to mountain biking vs. hiking, but there was a negative relationship between wildlife body size and response. We determined the area of influence along trails and off-trail transects by examining each species' probability of flushing as perpendicular distance away from a trail increased. All three species exhibited a 70% probability of flushing from on-trail recreationists within 100 m from trails. Mule deer showed a 96% probability of flushing within 100 m of recreationists located off trails; their probability of flushing did not drop to 70% until perpendicular distance reached 390 m. We calculated the area around existing trails on Antelope Island that may be impacted by recreationists on those trails. Based on a 200-m ''area of influence,'' 8.0 km (7%) of the island was potentially unsuitable for wildlife due to disturbance from recreation. Few studies have examined how recreationists perceive their effects on wildlife, although this has implications for their behavior on public lands. We surveyed 640 backcountry trail users on Antelope Island to investigate their perceptions of the effects of recreation on wildlife. Approximately 50% of recreationists felt that recreation was not having a negative effect on wildlife. In general, survey respondents perceived that it was acceptable to ap-proach wildlife more closely than our empirical data indicated wildlife would allow. Recrea-tionists also tended to blame other user groups for stress to wildlife rather than holding themselves responsible. The results of both the biological and human-dimensions aspects of our research have implications for the management of public lands where the continued coexistence of wildlife and recreation is a primary goal. Understanding wildlife responses to recreation and the ''area of influence'' of human activities may help managers judge whether wildlife pop-ulations are experiencing stress due to interactions with humans, and may aid in tailoring recreation plans to minimize long-term effects to wildlife from disturbance. Knowledge of recreationists' perceptions and beliefs regarding their effects on wildlife may also assist public lands managers in encouraging positive visitor behaviors around wildlife.
Article
Full-text available
Wildlife-human interactions are increasing in prevalence as urban sprawl continues to encroach into rural areas. Once considered to be unsuitable habitat for most wildlife species, urban/suburban areas now host an array of wildlife populations, many of which were previously restricted to rural or pristine habitats. The presence of some wildlife species in close proximity to dense human populations can create conflict, forcing resource managers to address issues relating to urban wildlife. However, evidence suggests that wildlife residing in urban areas may not exhibit the same life history traits as their rural counterparts because of adaptation to human-induced stresses. This creates difficulty for biologists or managers that must address problems associated with urban wildlife. Population control or mitigation efforts aimed at urban wildlife require detailed knowledge of the habits of wildlife populations in urban areas. This paper describes the history of wildlife in urban areas, provides examples of wildlife populations that have modified their behavior as an adaptation to urban stresses, and discusses the challenges that resource managers face when dealing with urban wildlife.
Article
Full-text available
Two species of tree squirrel inhabit the Chicago region, the fox (Sciurus niger) and gray (S. caroliniensis) squirrel. Chicago residents submitted squirrel observations and associated landscape variables via a Website, allowing us to map squirrel distributions. Data were analyzed for patterns of correlation. At a smaller scale, we did a foot survey of fox and gray squirrels in the suburb of Oak Park, replicating an earlier study and comparing results. Gray squirrels were associated with densely populated areas, parks and campuses, fox squirrels with suburban areas. Compared to gray squirrels, fox squirrels were more likely to be observed in areas of high cat density. In the suburb of Oak Park, the current trend seems to be an extension of gray squirrel distribution and a decrease in fox squirrel distribution. Our study provides support for the idea that fox and gray squirrel coexistence is facilitated by a trade-off between managing the cost of predation and foraging efficiency, gray squirrels out-competing fox squirrels in areas of high food and low predator (or pet) density.
Article
Full-text available
The relationship between preflight risk assessment by prey and the escape behaviors they perform while fleeing from predators is relatively unexplored. To examine this relationship, a human observer approached groups of Columbian black-tailed deer (Odocoileus hemionus columbianus), varying his behavior to simulate more or less threatening behavior. We measured the focal deer's angle of escape, distance moved during flight, duration of trotting and stotting behavior, and change in elevation during flight. Analyses revealed positive relationships between the distance moved during flight and the distance at which they fled. When flight was initiated when the approacher was close, deer fled relatively shorter distances and took flight paths at more acute angles, a property that would force a real predator to change direction suddenly. Our results indicate that deer do not compensate for allowing the observer to approach more closely by fleeing greater distances. Rather, distance moved and flight initiation distance are linked by level of reactivity and habituation: more reactive or less habituated deer both flee at a greater distance and move away to a greater distance during flight. More threatening behavior by the approacher led to longer durations of rapid flight behavior (e.g., trotting and stotting), and deer tended to flee uphill and into taller vegetation, using these landscape features as refuge from danger. Finally, we provide the first evidence for Pitcher's untested "antiambush" hypothesis for the function of stotting and discuss its significance. In general, both preflight predator behavior and habitat features influence both duration and direction of escape. Copyright 2007, Oxford University Press.
Article
Full-text available
"A growing number of studies quantify the impact of nonlethal human disturbance on the behavior and reproductive success of animals. Athough many are well designed and analytically sophisticated, most lack a theoretical framework for making predictions and for understanding why particular responses occur. Behavioral ecologists have recently begun to fill this theoretical vacuum by applying economic models of antipredator behavior to disturbance studies. In this emerging paradigm, predation and nonlethal disturbance stimuli create similar trade-offs between avoiding perceived risk and other fitness-enhancing activities, such as feeding, parental care, or mating. A vast literature supports the hypothesis that antipredator behavior has a cost to other activities, and that this trade-off is optimized when investment in antipredator behavior tracks short-term changes in predation risk. Prey have evolved antipredator responses to generalized threatening stimuli, such as loud noises and rapidly approaching objects. Thus, when encountering disturbance stimuli ranging from the dramatic, lowflying helicopter to the quiet wildlife photographer, animal responses are likely to follow the same economic principles used by prey encountering predators. Some authors have argued that, similar to predation risk, disturbance stimuli can indirectly affect fitness and population dynamics via the energetic and lost opportunity costs of risk avoidance. We elaborate on this argument by discussing why, from an evolutionary perspective, disturbance stimuli should be analogous to predation risk. We then consider disturbance effects on the behavior of individuals--vigilance, fleeing, habitat selection, mating displays, and parental investment--as well as indirect effects on populations and communities. A wider application of predation risk theory to disturbance studies should increase the generality of predictions and make mitigation more effective without over-regulating human activities."
Article
Full-text available
The amount of risk animals perceive in a given circumstance (i.e. their degree of 'fear') is a difficult motivational state to study. While many studies have used flight initiation distance as a proxy for fearfulness and examined the factors influencing the decision to flee, there is no general understanding of the relative importance of these factors. By identifying factors with large effect sizes, we can determine whether anti-predator strategies reduce fear, and we gain a unique perspective on the coevolution of predator and anti-predator behaviour. Based on an extensive review and formal meta-analysis, we found that predator traits that were associated with greater risk (speed, size, directness of approach), increased prey distance to refuge and experience with predators consistently amplified the perception of risk (in terms of flight initiation distance). While fish tolerated closer approach when in larger schools, other taxa had greater flight initiation distances when in larger groups. The presence of armoured and cryptic morphologies decreased perception of risk, but body temperature in lizards had no robust effect on flight initiation distance. We find that selection generally acts on prey to be sensitive to predator behaviour, as well as on prey to modify their behaviour and morphology.
Article
Full-text available
Ecotourism is increasing worldwide; hence, it is important to know how wildlife are affected behaviorally and physiologically by human visitation. We studied the effects of human visitation on the Magellanic Penguins (Spheniscus magellanicus) at Punta Tombo, Argentina, by monitoring changes in defensive head turns and plasma corticosterone (a hormone secreted in response to stress) for penguins with and without a history of tourist visitation. Habituation to human visitation was rapid. In penguins with no previous exposure to tourists, the number of defensive head turns and level of plasma corticosterone decreased significantly within 5 days of one 15-minute visit/day. Penguins living in tourist-visited and undisturbed areas secreted more corticosterone when captured and restrained than penguins visited by a person. Penguins in tourist areas, however did not show as strong a corticosterone response to capture and restraint as did penguins in areas without tourists. This difference was due to a decreased capability of the adrenocortical tissue to secrete corticosterone in tourist-visited birds. Although our data show no direct negative effects of tourism on Magellanic Penguins at Punta Tombo, consequences of a modification of physiological capabilities (e.g., adrenocortical function) may not become apparent until much later in life. The physiological differences between tourist-visited and undisturbed groups of Magellanic Penguins emphasize the importance of monitoring the effects of anthropogenic disturbances on wildlife at multiple levels.
Article
Full-text available
If changes in animal behavior resulting from direct human disturbance negatively affect the persistence of a given species or population, then these behavioral changes must necessarily lead to reduced demographic performance. We tested for the effects of human disturbance on Olympic marmots (Marmota olympus), a large ground-dwelling squirrel that has disappeared from several areas where recreation levels are high. We assessed the degree to which antipredator and foraging behavior and demographic rates (survival and reproduction) differed between sites with high recreation levels (high use) and those with little or no recreation (low use). Compared with the marmots at low-use sites, marmots at high-use sites displayed significantly reduced responses to human approach, which could be construed as successful accommodation of disturbance or as a decrease in predator awareness. The marmots at high-use sites also looked up more often while foraging, which suggests an increased wariness. Marmots at both types of sites had comparable reproductive and survival rates and were in similar body condition. Until now, the supposition that marmots can adjust their behavior to avoid negative demographic consequences when confronted with heavy tourism has been based on potentially ambiguous behavioral data. Our results support this hypothesis in the case of Olympic marmots and demonstrate the importance of considering demographic data when evaluating the impacts of recreation on animal populations.
Article
Full-text available
Dog walking is among the world's most popular recreational activities, attracting millions of people to natural areas each year with diverse benefits to human and canine health. But conservation managers often ban dog walking from natural areas fearing that wildlife will see dogs as potential predators and abandon their natural habitats, resulting in outcry at the restricted access to public land. Arguments are passionate on both sides and debate has remained subjective and unresolved because experimental evidence of the ecological impacts of dog walking has been lacking. Here we show that dog walking in woodland leads to a 35% reduction in bird diversity and 41% reduction in abundance, both in areas where dog walking is common and where dogs are prohibited. These results argue against access by dog walkers to sensitive conservation areas.
Article
Responses by Odocoileus hemionus to people in the Junction Butte State Wildlife Area, N-central Colorado, were longer in duration, involved running more frequently and were greater in energy expenditure. Minimal responses would require people afoot to remain >334m and snowmobiles >470m away from deer. Preventing locomotor responses by deer would require these distances to be >191 and >133m, respectively.-P.J.Jarvis
Article
ABSTRACT We measured the responses of two grassland passerines, one forest passerine, and one large mammal exposed to recreational treatments both on- and off-trail, including a pedestrian alone, a pedestrian accompanied by a dog-on-leash, and a dog alone. Responses measured included flush response (whether the animal flushed or not), flush distance (distance between disturbance and animal when flushed), distance of flush (distance the animal moved after flushing). All wildlife species in our study exhibited greater responses when the treatment occurred off-trail than when on-trail. In the grasslands, the dog-alone treatment elicited the least response by vesper sparrows (Pooecetes gramineus) and western meadowlarks (Sturnella neglects), whereas pedestrian-alone and pedestrian accompanied by a dog-on-leash elicited greater responses. In the forest, American robins (Turdus migratorius) responded similarly to @,, recreationist-wildlife conflicts (Knight and Gutzwiller 1995). As a result, natural-lands managers are showing increasing awareness of *,1
Article
Habitat choice and interactions of foraging shorebirds and gulls were studied at a migratory stopover in Delaware Bay, New Jersey. Foraging, vigilance, aggressive behavior, and habitat choice of shorebirds were affected by the presence of gulls. There were significant differences in the time each species devoted to actively feeding; knots spent significantly less time foraging than did the other species. Birds congregated in the habitats where their foraging rates were the highest. When turnstones and laughing gulls fed in larger conspecific flocks, they had higher foraging times. Red knots were most aggressive toward laughing gulls, turnstones were most aggressive toward herring gulls, sanderlings were most aggressive toward turnstones, and semipalmated sandpipers were most aggressive toward knots. There were significant differences in habitat use: 1) Gulls and turnstones were more abundant along the tide line, 2) turnstones were more abundant on the upper beach, 3) semipalmated sandpipers and turnstones were more abundant on sandbars, 4) only gulls fed on the beach mud, and 5) laughing gulls and semipalmated sandpipers were more common along creeks than were the other species. Within 5 minutes of a human disturbance, gulls returned to predisturbance levels, while the shorebirds did not. Shorebirds responded most strongly to the presence of dogs than to other disturbances and did not return to beaches following a disturbance by a dog. These observations suggest that there may be some competition for foraging space among foraging species, especially between the shorebirds and the larger gulls, that human disturbance affects shorebirds more strongly than gulls, and that shorebirds and gulls use the habitats differently. The data can be used to manage human disturbance and to protect habitats where the shorebirds have the highest foraging rates, but the least exposure to gulls.
Article
Gray squirrels (Sciurus carolinensis) typically run to the nearest tree to escape from predators they encounter while foraging on the ground. As the risk of capture increases with distance from the refuge tree, squirrels feeding far from trees should have greater flight initiation distances than those feeding closer by. This prediction was confirmed: flight initiation distance in response to a motorized model predator (a cat) increased as distance to refuge increased. This could not be attributed to any effect of distance to refuge on vigilance.
Article
In the region of First near Grindelwald (Swiss alps) alpine marmots Marmota marmota reacted differently to various forms of hiking tourism. The smallest reaction was recorded when hikers kept to trails. The reaction increased with cross-country hiking and was even greater when the main burrows of the animals were crossed. The severest reaction was seen in experiments with dogs on a long leash.It can be concluded that the predictability and potential threat (dogs) are decisive factors in the reactions of marmots to different forms of hiking.
Article
House sparrows (Passer domesticus) feeding away from protective cover decrease their level of vigilance as group size increases. In contrast to recent studies, however, their level of vigilance decreases when feeding farther from cover or in the presence of visual obstructions. These apparent discrepancies reflect the potential complexity in the response of vigilance to various aspects of the risk of predation; scanning need not necessarily increase with the risk of predation. Much work as to the exact nature of the factors influencing vigilance remains to be done before we can fully understand its response to various environmental manipulations.
Article
Examined the effects of obstructive and protective cover on vigilance of house sparrows and starlings. Feeding patches were provided, one with protective cover (a frame filled with plant cuttings forming a loose hedge which did not severely restrict visibility) and one with obstructive cover (a frame covered by a solid wooden board on the side on which the birds fed). Vigilance, defined as the proportion of observations during which an individual was vigilant, increased with distance to protective cover, but decreased with distance to obstructive cover, for both sparrows and starlings. After distance to cover, the strongest effect on vigilance was total flock size. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
The rapid response of animals to changes in predation risk has allowed behavioral ecologists to learn much about antipredator decision making. A largely unappreciated aspect of such decision making, however, is that it may be fundamentally driven by the very thing that allows it to be so readily studied: temporal variation in risk. We show theoretically that temporal variability in risk leaves animals with the problem of allocating feeding and antipredator efforts across different risk situations. Our analysis suggests that an animal should exhibit its greatest antipredator behavior in high-risk situations that are brief and infrequent. An animal should also allocate more antipredator effort to high-risk situations and more feeding to low-risk situations, with an increase in the relative degree of risk in high-risk situations. However, the need to feed leaves an animal with little choice but to decrease its allocation of antipredator effort to high-risk situations as they become more frequent or length
Article
Summary • Human disturbance has been associated with declines in breeding success in numerous species and is of general concern to conservationists. However, the current framework for predicting and minimizing disturbance effects is weak and there is considerable uncertainty about why animals are disturbed by people in the first place. • We developed a behavioural model of perceived predation risk as a framework for understanding the effects of disturbance on cliff-nesting birds. This encompassed the concept that the effects of disturbance should increase with increasing numbers of visitors, and decrease with distance from the nest, an insight ignored in current conservation practice. • The predictions of this model were tested using field data on nesting success in two species of seabird, kittiwake Rissa tridactyla and guillemot Uria aalge. Statistical models of nesting success in both species suggested that perceived predation risk is a good predictor of the effects of disturbance. • Synthesis and applications. Our findings suggest that fixed set-back distances and buffer zones are likely to be inappropriate conservation measures in situations where the numbers of visitors to wildlife areas fluctuates spatially and temporally, as is generally the case. In managing access to wildlife areas there is a need to ensure that larger parties of visitors are kept further away from the nesting areas of vulnerable species or that set-back distances are determined for the largest party likely to visit the site. Journal of Applied Ecology (2004) 41, 335 –343
Article
The strength of an animal's behavioural response to human presence has often been used as an index of an animal's susceptibility to disturbance. However, if behavioural responsiveness is positively related to the animal's condition, this may be an inappropriate index, as individuals showing little or no response may in fact be those with most to lose from changing their behaviour. We tested the link between individual state and responsiveness by manipulating condition via the provision of supplementary food for turnstones, Arenaria interpres, on rocky shores. Birds at one site were fed 450 g of mealworms at low tide every day for 3 days while birds at another site acted as a control. On the fourth day, using a standardized disturbance protocol, we recorded flush distances, flight lengths and the amount of time between predator scans for birds in both flocks. After a break of 3 days, the treatments were then swapped between sites and the procedure repeated for a total of six trials. Birds whose condition had been enhanced showed greater responsiveness to standardized human disturbance, flying away at greater distances from the observer, scanning more frequently for predators and flying further when flushed. These findings suggest that our current management of the impact of human disturbance may be based on inaccurate assessments of vulnerability, and we discuss the implications of this for refuge provision.
Article
Human recreation has immediate and long-term impacts on wildlife, and exposure to recreational activities might be particularly high in urban systems. We investigated the relationship between human recreation and the spatial and temporal activity patterns of large mammals in an urban nature reserve. Data from remotely triggered infra-red cameras (1999–2001) were used to assess activity for bobcat, coyote, mule deer, humans, and domestic dogs along paths in the Nature Reserve of Orange County (NROC), California. Forty-nine camera sites established across the NROC yielded 16,722 images of humans, dogs, and our three target large mammal species during 4232 observation nights. Results suggest that bobcats, and to a lesser degree coyotes, exhibited both spatial and temporal displacement in response to human recreation. Bobcats were not only detected less frequently along trails with higher human activity, but also appeared to shift their daily activity patterns to become more nocturnal in high human use areas; negative associations between bobcat and human activity were particularly evident for bikers, hikers, and domestic dogs. In general, both bobcats and coyotes displayed a relatively wide range of activity levels at sites with low human use, but a lower and markedly restricted range of activity at those sites with the highest levels of recreation. Although we did not find a clear and consistent pattern of avoidance of human recreation by deer, the probability of detecting deer during the day was lower with increasing levels of human recreation. Future studies that experimentally investigate the impacts of recreationists on wildlife, as well as relate behavioral responses to survival and reproduction, will allow further insight of the effects of urban recreation on large mammal populations.
Article
Previous studies of vigilance have concentrated on situations where the prey species has an unimpaired view of its surroundings. Here the effects of reduced visibility caused by objects adjacent to the prey are studied in two species of shorebird. A reduction in visibility causes an increase in the level of vigilance, indicating an increase in vulnerability despite the greater degree of camouflaging. This increase is due to individuals being less able to see both approaching predators and their neighbours. Turnstones, Arenaria interpres, and purple sandpipers, Calidris maritima, show very similar increases in the level of vigilance with decreasing visibility, but achieve these increases by different means: turnstones lengthen the duration of each vigilant scan, while purple sandpipers scan more often. Increasing scanning rate produces a shortened interval between scans, which reduces the risk of being caught unawares by an approaching predator. However, it may also reduce feeding efficiency, and it is suggested that this might be more serious in turnstones due to greater handling times for food items, so causing them to adopt a different strategy to increase vigilance.