Decreased vigilance or habituation to humans? Mechanisms on increased boldness in urban animals

Abstract 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.

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Increasing corvid tolerance to humans in urban ecosystems with increasing latitude

Biological Communications ◽

10.21638/spbu03.2019.404 ◽

2020 ◽

Vol 64 (4) ◽

Author(s):

Nadezhda Poddubnaya ◽

Tatyana Korotkova ◽

Polina Vanicheva

Keyword(s):

Environmental Factors ◽

Human Disturbance ◽

Urban Ecosystems ◽

Flight Initiation Distance ◽

Protection Measures ◽

Non Invasive ◽

Alert Distance ◽

Behaviour Changes ◽

Hooded Crows ◽

Flight Initiation

The rapid growth of cities causes behaviour changes in birds in response to urban environmental factors. The avian response to human disturbance has recently been studied by a non-invasive research tool as an alert distance (AD) and a flight initiation distance (FID) assessment. The tolerance of hooded crows (n = 395), jackdaws (n = 394) and rooks (n = 169) to humans was assessed by AD and FID. It was shown that the FID of all species is maximal during the summer, when the parents send clear “danger—fly away” signals to the young and the birds fly away. The AD and FID of the three species reliably correlates with the season. Rooks showed FID species-specificity in seven cities of Eastern Europe. Comparison of the attitude of birds to people in cities that have similarities in human culture showed that tolerance increases with increasing latitude in all species and is statistically significant only in the jackdaw. This should be taken into account in environmental protection measures.

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Characteristics of urban environments and novel problem-solving performance in Eurasian red squirrels

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.2832 ◽

2021 ◽

Vol 288 (1947) ◽

Author(s):

Pizza Ka Yee Chow ◽

Kenta Uchida ◽

Auguste M. P. von Bayern ◽

Itsuro Koizumi

Keyword(s):

Problem Solving ◽

Population Size ◽

Human Disturbance ◽

Population Level ◽

Urban Environments ◽

The Novel ◽

Environmental Characteristics ◽

Red Squirrels ◽

Individual Level ◽

The Individual

Urban environments can be deemed ‘harsh’ for some wildlife species, but individuals frequently show behavioural flexibility to cope with challenges and demands posed by life in the city. For example, urban animals often show better performance in solving novel problems than rural conspecifics, which helps when using novel resources under human-modified environments. However, which characteristics of urban environments fine-tune novel problem-solving performance, and their relative importance, remain unclear. Here, we examined how four urban environmental characteristics (direct human disturbance, indirect human disturbance, size of green coverage and squirrel population size) may potentially influence novel problem-solving performance of a successful ‘urban dweller’, the Eurasian red squirrel, by presenting them with a novel food-extraction problem. We found that increased direct human disturbance, indirect human disturbance and a higher squirrel population size decreased the proportion of solving success at the population level. At the individual level, an increase in squirrel population size decreased the latency to successfully solve the novel problem the first time. More importantly, increased direct human disturbance, squirrel population size and experience with the novel problem decreased problem-solving time over time. These findings highlight that some urban environmental characteristics shape two phenotypic extremes in the behaviour-flexibility spectrum: individuals either demonstrated enhanced learning or they failed to solve the novel problem.

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Continent-wide genomic signatures of adaptation to urbanisation in a songbird across Europe

Nature Communications ◽

10.1038/s41467-021-23027-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Pablo Salmón ◽

Arne Jacobs ◽

Dag Ahrén ◽

Clotilde Biard ◽

Niels J. Dingemanse ◽

...

Keyword(s):

Parus Major ◽

Urban Environments ◽

Rural Site ◽

Neural Function ◽

Selective Sweeps ◽

Genetic Changes ◽

Ample Evidence ◽

Genomic Signatures ◽

Core Set ◽

Urban Adaptation

AbstractUrbanisation is increasing worldwide, and there is now ample evidence of phenotypic changes in wild organisms in response to this novel environment. Yet, the genetic changes and genomic architecture underlying these adaptations are poorly understood. Here, we genotype 192 great tits (Parus major) from nine European cities, each paired with an adjacent rural site, to address this major knowledge gap in our understanding of wildlife urban adaptation. We find that a combination of polygenic allele frequency shifts and recurrent selective sweeps are associated with the adaptation of great tits to urban environments. While haplotypes under selection are rarely shared across urban populations, selective sweeps occur within the same genes, mostly linked to neural function and development. Collectively, we show that urban adaptation in a widespread songbird occurs through unique and shared selective sweeps in a core-set of behaviour-linked genes.

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Common notions and composite collaborations: Thinking with Spinoza to design urban infrastructures for human and wild cohabitants

Interstices: Journal of Architecture and Related Arts ◽

10.24135/ijara.vi.670 ◽

2021 ◽

pp. 20-31

Author(s):

Sue Ruddick

Keyword(s):

Urban Design ◽

Urban Environments ◽

Urban Wildlife ◽

Wildlife Habitat ◽

Composite Body ◽

Common Notion ◽

The City ◽

Over Time

This paper explores the ways in which we might construct urban environments that are responsible to the needs of more than just human cohabitants. Drawing on Spinoza’s common notion and attentive to the possibilities of socio-natures that both construct and respond to the habitat needs of urban wildlife, I look at how urban design and wildlife habitat might be thought and planned together as a human/non-human composite, invoking a complex spatial and temporal choreography which serves divergent needs. Drawing on examples of urban design in Toronto, Canada, this paper offers a way to think of the city as a composite body in Spinoza’s terms, to become open to an awareness of the city as a composition of forces—a choreography of bodies that are constantly interweaving and overflowing imagined boundaries, struggles that are fought as much over time as space, the accommodation of the temporalities and spatialities of other life processes, other rhythms and cycles that would, without a recalibration, sync uneasily with the pacing and spacing of human requirements.

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The finer points of urban adaptation: intraspecific variation in lizard claw morphology

Biological Journal of the Linnean Society ◽

10.1093/biolinnean/blaa123 ◽

2020 ◽

Vol 131 (2) ◽

pp. 304-318

Author(s):

Cleo H Falvey ◽

Kevin J Aviles-Rodriguez ◽

Travis J Hagey ◽

Kristin M Winchell

Keyword(s):

Natural Experiment ◽

Urban Environments ◽

Phenotypic Change ◽

Structural Environment ◽

Claw Morphology ◽

Anthropogenic Substrates ◽

Urban Adaptation ◽

Shape Changes ◽

Forest Habitats ◽

Claw Shape

Abstract Human activity drastically transforms landscapes, generating novel habitats to which species must adaptively respond. Consequently, urbanization is increasingly recognized as a driver of phenotypic change. The structural environment of urban habitats presents a replicated natural experiment to examine trait–environment relationships and phenotypic variation related to locomotion. We use geometric morphometrics to examine claw morphology of five species of Anolis lizards in urban and forest habitats. We find that urban lizards undergo a shift in claw shape in the same direction but varying magnitude across species. Urban claws are overall taller, less curved, less pointed and shorter in length than those of forest lizards. These differences may enable more effective attachment or reduce interference with toepad function on smooth anthropogenic substrates. We also find an increase in shape disparity, a measurement of variation, in urban populations, suggesting relaxed selection or niche expansion rather than directional selection. This study expands our understanding of the relatively understudied trait of claw morphology and adds to a growing number of studies demonstrating phenotypic changes in urban lizards. The consistency in the direction of the shape changes we observed supports the intriguing possibility that urban environments may lead to predictable convergent adaptive change.

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Optimal escape theory predicts escape behaviors beyond flight initiation distance: risk assessment and escape by striped plateau lizards Sceloporus virgatus

Current Zoology ◽

10.1093/czoolo/55.2.123 ◽

2009 ◽

Vol 55 (2) ◽

pp. 123-131 ◽

Cited By ~ 32

Author(s):

William E. Cooper

Keyword(s):

Risk Factors ◽

Risk Assessment ◽

Predation Risk ◽

Flight Initiation Distance ◽

Risk Levels ◽

Escape Theory ◽

Growing Body ◽

Sceloporus Virgatus ◽

Escape Behaviors ◽

Flight Initiation

Abstract Escape theory predicts that flight initiation distance (FID = distance between predator and prey when escape begins) is longer when risk is greater and shorter when escape is more costly. A few tests suggest that escape theory applies to distance fled. Escape models have not addressed stochastic variables, such as probability of fleeing and of entering refuge, but their economic logic might be applicable. Experiments on several risk factors in the lizard Sceloporus virgatus confirmed all predictions for the above escape variables. FID was greater when approach was faster and more direct, for lizards on ground than on trees, for lizards rarely exposed to humans, for the second of two approaches, and when the predator turned toward lizards rather than away. Lizards fled further during rapid and second consecutive approaches. They were more likely to flee when approached directly, when a predator turned toward them, and during second approaches. They were more likely to enter refuge when approached rapidly. A novel finding is that perch height in trees was unrelated to FID because lizards escaped by moving out of sight, then moving up or down unpredictably. These findings add to a growing body of evidence supporting predictions of escape theory for FID and distance fled. They show that two probabilistic aspects of escape are predictable based on relative predation risk levels. Because individuals differ in boldness, the assessed optimal FID and threshold risks for fleeing and entering refuge are exceeded for an increasing proportion of individuals as risk increases.

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Do squirrels in human disturbed areas become habituated to humans? A measure of flight initiation distance across disturbance gradients

USURJ University of Saskatchewan Undergraduate Research Journal ◽

10.32396/usurj.v1i2.121 ◽

2015 ◽

Vol 1 (2) ◽

Author(s):

Megan D Bjordal

Keyword(s):

North American ◽

Human Disturbance ◽

Tamiasciurus Hudsonicus ◽

Flight Initiation Distance ◽

Natural Habitats ◽

Red Squirrels ◽

Disturbed Areas ◽

Significant Difference ◽

North American Red Squirrels ◽

Flight Initiation

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.

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Shyer and larger bird species show more reduced fear of humans when living in urban environments

Biology Letters ◽

10.1098/rsbl.2017.0730 ◽

2018 ◽

Vol 14 (4) ◽

pp. 20170730 ◽

Cited By ~ 4

Author(s):

Javier delBarco-Trillo

Keyword(s):

Bird Species ◽

Generalized Least Squares ◽

Urban Environments ◽

Phenotypic Traits ◽

Flight Initiation Distance ◽

Natural Habitats ◽

Urban Populations ◽

Rural And Urban ◽

Consistent Response ◽

Flight Initiation

As the natural habitats of many species are degraded or disappear, there is scope for these species to be established in urban habitats. To ease the establishment and maintenance of urban populations of more species we need to better understand what degree of phenotypical change to expect as different species transition into urban environments. During the first stages of urban colonization, behavioural changes such as an increase in boldness are particularly important. A consistent response in urban populations is to decrease the distance at which individuals flee from an approaching human (flight initiation distance, or FID). Performing a phylogenetic generalized least-squares (PGLS) analysis on 130 avian species, I found that the largest changes in FID between rural and urban populations occur in species that are larger-bodied and naturally shy (higher rural FID), two phenotypic traits that are not normally associated with urban colonizers. More unlikely species may thus be able to colonize urban environments, especially if we design cities in ways that promote such urban colonizations.

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Humanization of wildlife gut microbiota in urban environments

10.1101/2022.01.05.475040 ◽

2022 ◽

Author(s):

Brian A. Dillard ◽

Albert K. Chung ◽

Alex R. Gunderson ◽

Shane C. Campbell-Staton ◽

Andrew H. Moeller

Keyword(s):

Gut Microbiota ◽

Canis Latrans ◽

Urban Environments ◽

Urban Wildlife ◽

Human Populations ◽

Urban Populations ◽

Bacterial Lineages

Urbanization is rapidly altering Earth’s environments, demanding investigations of the impacts on resident wildlife. Here, we show that urban populations of coyotes (Canis latrans) and crested anole lizards (Anolis cristatellus) acquire gut microbiota constituents found in humans, including the gut bacterial lineages most significantly associated with urbanization in humans (e.g., Bacteroides). Comparisons of urban and rural wildlife and human populations revealed significant convergence of the gut microbiota among urban host populations. Remarkably, all microbial lineages found in humans that were overrepresented in urban wildlife relative to rural wildlife were also overrepresented in urban humans relative to rural humans. These results indicate parallel effects of urbanization on human and wildlife gut microbiota and suggest spillover of bacteria from humans into wildlife in cities.

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