human disturbance

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Who’s the big bad wolf afraid of? Investigating how humans affect the predatory behavior of wolves

/ Beth Preston / Leave a comment
This blog post is provided by Kristin Barker and tells the #StoryBehindthePaper for the paper “Large carnivores avoid humans while prioritizing prey acquisition in anthropogenic areas“, which was recently published in Journal of Animal Ecology. In the study, they investigate the impact of human activity on the behaviour of grey wolves, finding a nuanced response to different human influences depending on the context.

Right now, populations of large carnivores like grizzly bears and grey wolves are recovering across the globe. There’s a common story in ecology that these predators deliberately avoid humans, and many of our key ecological theories hinge on this story. For example, we attribute the increasing use of human areas by ungulates (hooved mammals) to the reduced predation risk afforded by large carnivores’ avoidance of humans. But livestock producers and others who live in carnivore recovery areas share stories of large predators killing and eating prey right in front of humans with no apparent avoidance response.

A wolf stands on the National Elk Refuge in Jackson Hole, Wyoming, USA. (Photo credit: Mark Gocke, Wyoming Game and Fish Department)

To reconcile the disparity between our expectation that large carnivores should avoid humans and the reality that sometimes they don’t, we need to understand how these animals perceive and respond to humans. Are large carnivores scared of humans only if we directly threaten them, for instance by hunting? Or are they not scared at all, but rather just generally disturbed by human activity, in which case we would expect a weaker but more generalized avoidance of humans? It’s also possible that carnivores are attracted to human areas where ungulate prey concentrate in predictable places and times, but it’s not clear whether this potential food benefit might outweigh the costs of potentially interacting with humans. Teasing apart carnivore perception of humans could help resolve some of the uncertainty around carnivore responses to humans in different contexts. 

To answer these questions, and to investigate whether human-induced behavioral changes in large carnivores affect the risk of predation for their ungulate prey, we launched a new field campaign in the southeastern Greater Yellowstone Ecosystem, USA. Over the course of three winters we skied, snowshoed, waded, and snowmobiled to more than 1000 potential wolf kill sites. We then contrasted characteristics of the 170 wolf kills we found with those of matched non-kill sites to quantify how predation risk changed as a function of human influences, while controlling for key environmental factors. Specifically, we evaluated the effects of roads, trails, and human-run ungulate feedgrounds, and we also investigated whether wolves responded more strongly to these influences if they had previously been hunted by humans and/or if it was during the day when humans were most active.

Field technician Celeste Governale bootpacks along a ridge to access a wolf kill site in southeastern Jackson Hole. (Photo credit: Kristin Barker)

We found that wolves did change their predatory behavior in response to humans, but they didn’t unequivocally perceive humans as either scary, disturbing, or beneficial. Instead, wolves in our study area actively distinguished between different types of human influences based on the immediate costs and benefits of each. For example, we found opposite responses of wolves to roads and trails. Wolves preferentially made kills far from paved, plowed roads but close to unplowed oversnow trails, despite plowed roads making it much easier to travel through the snowy landscape. However, wolf response to human influences was much weaker – and in some cases nonexistent – in areas where prey availability was particularly low. Furthermore, despite their preference for using unplowed trails to access their prey, wolves avoided killing prey near trails during the day when humans were most likely to be using them. 

Struggling to ski uphill in the Gros Ventre River drainage, field technician Celeste Governale becomes intimately acquainted with the influence of snow depth on animal movement. (Photo credit: Kristin Barker)

This nuanced response of wolves to different human influences helps clear up superficially incongruous results from other studies and personal observations. Based on our finding that wolves actively differentiate between the immediate risks and rewards of multiple simultaneous human influences, it is not surprising that wolves respond very differently to humans in different contexts. Our work suggests that the degree to which wolves alter their predatory behavior hinges on the availability of ungulate prey in conjunction with the intensity or predictability of human use. In particular, in areas where prey are scarce, wolves may be unlikely to prioritize avoiding humans over acquiring prey despite their general avoidance of human activity. In the next phase of our research, we are building on these findings to investigate how the responses of wolves to humans can directly and indirectly affect populations of their native prey.

Field technician Hannah Booth performs a necropsy at a potential wolf kill site along the Snake River. (Photo credit: Becca Lyon)

As populations of large carnivores continue to recover across the globe, they will inevitably continue to expand into human-dominated areas. Wildlife managers, conservationists, policymakers, and local stakeholders all have a vested interest in anticipating and responding to the ecological and socioeconomic effects of carnivore recovery. By unveiling some of the nuance behind wolf response to humans, we hope our work can help inform strategies to mitigate concerns related to human-wildlife conflict, prey population dynamics, and undesirable ungulate distributions in human-dominated areas.

Wolves and elk share the landscape with humans in Jackson Hole, Wyoming (filmed by Mark Gocke of the Wyoming Fish and Game Department)
Read the paper

Read the full paper here: Barker, K J., Cole, E., Courtemanch, A., Dewey, S., Gustine, D., Mills, K., Stephenson, J., Wise, B., & Middleton, A D. (2023). Large carnivores avoid humans while prioritizing prey acquisition in anthropogenic areas. Journal of Animal Ecology, 00, 1– 12. https://doi.org/10.1111/1365-2656.13900

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Beyond simple habituation: Anthropogenic habitats influence the escape behavior of spur-winged lapwings in response to both human and non-human threats

/ Beth Preston / Leave a comment
This blog post is provided by Bar-Ziv Michael, Sofer Aran, Gorovoy Adel and Spiegel Orr and tells the #StoryBehindthePaper for the paper “Beyond simple habituation: Anthropogenic habitats influence the escape behavior of spur-winged lapwings in response to both human and non-human threats“, which was recently published in Journal of Animal Ecology. In their paper they use a unique “Jack-Truck” to simulate a jackal predator, and explore how lapwings respond to novel predators and humans.

לחצו כאן בשביל הבלוג בשפה העברית

Spur-winged lapwings (Vanellus spinosus) are monogamous birds that tend to stay with their partner all year round. During the breeding season they guard their nest and chicks with intimidating calls, attacking everything that get close with sharp spurs located on their wings. This species is considered to be one of the most common waders in Israel, and can be found in a variety of habitats, including natural habitats, as well as dense cities. This fact is quite surprising, considering that wader populations are declining worldwide due to the fact that they nest on the ground. Natural habitats across the world are being destroyed to make way for human needs, which in turn negatively affect a large number of species that cannot cope with the changes. Lapwings, on the other hand, not only represent a growing population, but they are also found to be able to nest and raise their chicks into adulthood in parks and even next to highways.

A couple of Spur-winged lapwings (Vanellus spinosus) in a built-up area. Lapwings occupy various settlements in the Harod Valley (north-east of Israel), and we explored how living in these habitats affects their escape behavior (Photo: Avichai Ran)

While some lapwings prefer to live next to human settlements, not all of them do. Most of the lapwings stay in more natural areas with fewer encounters with humans. Wild animals that live in proximity to humans usually present a bolder set of behaviors, which differ from populations of the same species that live in a more natural habitat. Those bolder responses can be a result of fear reduction toward humans (in other words, habituation to an urban environments), or alternatively present a larger effect that the urban environment creates (for example individuals with bolder personality reside in more urban settings).

A spur-winged lapwing in the town of Beit-She’an, keeping calm in face of passing pedestrians. Habituation to humans may affect their escape behavior and flight initiation distance (FID). (Photo: Avichai Ran)

A simple and well-known method to test boldness in field conditions is testing the animal’s flight initiation distance behaviour (or FID). Generally, animals that escape too early from an approaching threat will not be able to fully exploit their environment, while on the other hand those that are escaping too late might be at risk of getting caught by a predator. The behaviours animals present after their initial escapes are important as well, because more lethal predators may require a faster reaction, fleeing further away and finding a place to hide. Different predators also require different escape strategies, and while with one type of threat it is worthwhile escaping fast and far, in others it can be a burden. Those strategies can also differ between habitat types, for example, in urban settings individuals that are too scared and will flee from every person passing by, won’t be able to exploit this habitat properly and might prefer to forage in other areas.

A golden jackal (Canis aureus), one of the main predators for lapwings and their nests in the natural and agricultural habitats. We simulated an approaching jackal to generalize lapwings’ response beyond habituation to humans. (Photo: Michael Bar-Ziv)

In a recent paper in the Journal of Animal Ecology, we tested the escape behaviour of spur-winged lapwings. More specifically, we first looked at their flight initiation distance, their mode of escaping (by foot or flight), and finally what distance they fled. We tested those behaviors between three habitat types (human-dominated, water ponds, and fields), and compared them to two kinds of approaching predators (a human and a jackal). While humans are abundant in urban settings, jackals tend to be found in natural environments. Jackals also prey on lapwing nests, chicks, and potentially also on the adults. To mimic an approaching jackal, we used a taxidermy of a young jackal mounted on top of a camouflaged, off-road remotely controlled vehicle (named “Jack-Truck”). To find lapwings in the different environments, we searched for them while driving. We choose this strategy because lapwings tend to be less alert to driving vehicles, which made it easy to notice them without disturbing them. Once a lapwing was spotted, they were approached by a human, or a jackal and the escape sequences mentioned above were recorded.

Assembling the “Jack-Truck”, a jackal model used to simulate an approaching jackal. We used this Jack-Truck to determine if lapwings within settlements are merely more habituated to humans, or whether they are generally bolder in face of an approaching predator (Photo: Assaf Uzan).

The purpose of this experiment was to understand 1) if individuals found in urban setting show a general bolder response to approaching threats when compared to other habitats? And 2) if so, does this bolder response derive from simple habituation to humans, or does it represent a larger phenomenon (such as human settlements attracting generally bolder individuals)? If lapwings showed a stronger reaction to the jackal compared to a human in human-dominated environments it might hint towards habituation, because they were more afraid of a novel predator. On the other hand, having the same reaction to both predator types might suggest a deeper effect those habitats have over these animals.

Examining our first question, we found that lapwings from human-dominated habitats were bolder in most of the sequences of the escaping behavior. First, as expected, they presented a shorter FID when approached. Secondly, even after escaping they still presented bolder behaviors by fleeing to a shorter distance and more likely to escape by running (rather than flying). Interestingly, when considering our second question, we found that lapwings tested in human-dominant habitats presented a bolder respond to both a human as well as a jackal approaching. Those results show that lapwings not only present a bolder behavior in human settlements, but more importantly, it shows that habituation to humans cannot be the only explanation for the bolder response.

A group of spur-winged lapwings gathering near a construction site next to the town of Beit-She’an (Photo: Michael Bar-Ziv)

Those results can give us a hint of the effects human disturbance have on animals. Our paper shows that some individuals can become accustomed to human settlements, but it has a cost. To do so, they will need to reduce their fear response. This can be a dangerous strategy, because while most people will not try to harm them, once a more lethal predator approaches them, it could be more difficult for them to avoid this situation. In a fast-changing world that is becoming more urbanized, findings like these are essential for understanding the impact human-development has on wildlife populations and communities, even in species that at a first glance appear more resilient to those changes.

Read the paper

Read the full paper here: Bar-Ziv, M., Sofer, A., Gorovoy, A., & Spiegel, O. (2022). Beyond simple habituation: Anthropogenic habitats influence the escape behaviour of spur-winged lapwings in response to both human and non-human threats. Journal of Animal Ecology, 00, 1– 13. https://doi.org/10.1111/1365-2656.13858