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Impacts of dogs on wildlife and water quality

  • Metropolitan Regional Government

Abstract and Figures

Metro periodically reviews the science literature behind its natural resource policies to ensure policies are based on the most current science. Recently staff reviewed the scientific literature regarding the impacts of dogs on wildlife to inform Metro Regulatory Code Title 10.01, which excludes pets from most Metro properties. The only exceptions are service dogs, leashed dogs on some regional trails, Broughton Beach, boat ramps and properties managed by others through intergovernmental agreements that are integrated into larger parks where leashed dogs are allowed (e.g., Forest Park). Any human related activity can disturb wildlife. In order to meet Metro's dual goals of protecting natural resources and providing access to nature, Metro has tried to strategically locate trails in less sensitive habitat and to ensure that human activity is as non-disruptive as possible. Part of that strategy has been to allow public access, while limiting certain activities such as bringing dogs into natural areas. The evidence that dogs negatively impact wildlife is overwhelming. It is clear that people with dogs – on leash or off – are much more detrimental to wildlife than people without dogs. Dogs (Canis lupus familiaris) are considered to be a subspecies of wolves (Canis lupus), and wildlife perceive dogs as predators.(30) Impacts include: 1. Physical and temporal displacement – The presence of dogs causes wildlife to move away, temporarily or permanently reducing the amount of available habitat in which to feed, breed and rest. Animals become less active during the day to avoid dog interactions. Furthermore, the scent of dogs repels wildlife and the effects remain after the dogs are gone. 2. Disturbance and stress response – Animals are alarmed and cease their routine activities. This increases the amount of energy they use, while simultaneously reducing their opportunities to feed. Repeated stress causes long-term impacts on wildlife including reduced reproduction and growth, suppressed immune system and increased vulnerability to disease and parasites. 3. Indirect and direct mortality – Dogs transmit diseases (such as canine distemper and rabies) to and from wildlife. Loose dogs kill wildlife. 4. Human disease and water quality impacts - Dog waste pollutes water and transmits harmful parasites and diseases to people.
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The impacts of dogs on wildlife and water quality: A literature review
Compiled by Lori Hennings, Metro Parks and Nature, April 2016
Metro periodically reviews the science literature behind its natural resource policies to ensure policies
are based on the most current science. Recently staff reviewed the scientific literature regarding the
impacts of dogs on wildlife to inform Metro Regulatory Code Title 10.01, which excludes pets from most
Metro properties. The only exceptions are service dogs, leashed dogs on some regional trails, Broughton
Beach, boat ramps and properties managed by others through intergovernmental agreements that are
integrated into larger parks where leashed dogs are allowed (e.g., Forest Park).
Any human related activity can disturb wildlife. In order to meet Metro's dual goals of protecting natural
resources and providing access to nature, Metro has tried to strategically locate trails in less sensitive
habitat and to ensure that human activity is as non-disruptive as possible. Part of that strategy has been
to allow public access, while limiting certain activities such as bringing dogs into natural areas.
The evidence that dogs negatively impact wildlife is overwhelming. It is clear that people with dogs on
leash or off are much more detrimental to wildlife than people without dogs. Dogs (Canis lupus
familiaris) are considered to be a subspecies of wolves (Canis lupus), and wildlife perceive dogs as
predators.(30) Impacts include:
1. Physical and temporal displacement The presence of dogs causes wildlife to move away,
temporarily or permanently reducing the amount of available habitat in which to feed, breed
and rest. Animals become less active during the day to avoid dog interactions. Furthermore, the
scent of dogs repels wildlife and the effects remain after the dogs are gone.
2. Disturbance and stress response Animals are alarmed and cease their routine activities. This
increases the amount of energy they use, while simultaneously reducing their opportunities to
feed. Repeated stress causes long-term impacts on wildlife including reduced reproduction and
growth, suppressed immune system and increased vulnerability to disease and parasites.
3. Indirect and direct mortality Dogs transmit diseases (such as canine distemper and rabies) to
and from wildlife. Loose dogs kill wildlife.
4. Human disease and water quality impacts - Dog waste pollutes water and transmits harmful
parasites and diseases to people.
Metro owns 17,000 acres of parks and natural areas and does not allow dogs or other pets on the vast
majority of these lands. Exceptions include service animals, leashed dogs on some regional trails,
Broughton Beach, boat ramps and certain properties managed by others through intergovernmental
agreements that are integrated into larger parks where leashed dogs are allowed (e.g., Forest Park). The
policy that prohibits visitors from bringing pets to most of Metro’s managed parks and natural areas was
initiated by Multnomah County in the 1980s and continued in practice after Metro assumed
management of those parks in the early 1990s. After a review of the scientific literature and meaningful
public discourse, Metro formally adopted the pets policy into its code in 1997 (Metro Council Regulatory
code Title 10.01 adopted in Ordinance 96-659A).
To ensure this decision reflects the most up-to-date information, Metro staff examined 54 peer-
reviewed scientific journal articles and several research reports relating to the impacts of dogs in natural
areas, including numerous literature reviews on the impacts of various types of recreation on wildlife
and habitat.(10, 28, 42,54,61,63, 65,68,71,73,77) The results of our literature review are summarized below.
Displacement may be the most significant impact due to the amount of habitat affected. The presence
of dogs causes most wildlife to move away from an area, which temporarily or permanently reduces the
amount of functionally available habitat to wildlife. The research is clear that people with dogs disturb
wildlife more than humans alone.(5,10,33,38,39,41,44,61,68,69) These effects reduce a natural area’s carrying
capacity for wildlife, and also reduces wildlife viewing experiences for visitors.
Studies on a variety of wildlife in many countries and settings demonstrate that dogs along trails and in
natural areas significantly alter wildlife behavior.(9,33,39,41,49,53,58) A 2011 literature review found negative
dog effects in all 11 papers that examined such effects.(65) Studies demonstrate dog-specific impacts on
reptiles,(29,31,48) shorebirds and waterfowl,(24,32,51,69) songbirds,(5,9,10) small mammals,(33,39,56) deer, elk and
bighorn sheep,(4,36,38,44,49,59,63) and carnivores.(22,33,52,58)
A study in France found that two hikers disturbed an area of 3.7 hectares walking near wild sheep,
whereas two hikers with dogs disturbed 7.5 hectares around the sheep.(41) In Chicago, migratory
songbirds were less abundant in yards with dogs.(9) Dog walking in Australian woodlands led to a 35%
reduction in bird diversity and a 41% reduction in the overall number of birds.(5) The same study showed
some disturbance of birds by humans, but typically less than half that induced by dogs.
Studies in California and Colorado showed that bobcats avoided areas where dogs were present,
including spatial displacement(22,33,52) and temporal displacement in which bobcats switched to night
time for most activities.(22) The Colorado study also demonstrated significantly lower deer activity near
trails specifically in areas that allowed dogs, and this effect extended at least 100 meters off-trail.(33)
This negative effect was also true for small mammals including squirrels, rabbits, chipmunks and mice,
with the impact extending at least 50 meters off-trail.
Evidence suggests that some wildlife species can habituate to certain predictable, non-threatening
disturbances such as people walking on a trail in a natural area; this effectively lowers the stress
response. Part of this adaptation may be due to wildlife learning what is and isn’t a threat, and also
avoidance of hunters.(19,55,63,70) Habituated animals still react, but amount of habitat affected is not as
large.(55,56,63,70) However, dogs especially off-leash dogs may prevent wildlife habituation because
wildlife consistently see them as predators. Dog-specific disturbance has been studied for birds, with no
evidence of habituation even with leashed dogs, even where dog-walking was frequent; this effect was
much weaker for people without dogs.(5)
Even the scent of dog urine or feces can trigger wildlife to avoid an area. Therefore, the impacts of dog
presence can linger long after the dog is gone, even days later. One literature review found that
predator odors caused escape, avoidance, freezing, and altered behavior in a large suite of wildlife
species including scores of amphibian, reptile, bird, and mammal species from other studies.(30) The
scent of domestic dogs has been shown to repel American beaver (Castor Canadensis), mountain beaver
(Aplodontia rufa), deer (Odocoileus species), elk (Cerus elaphus), and a wide variety of wildlife native to
other countries.(20,30) Mountain beaver cause economic damage to young tree stands in the Pacific
Northwest, and foresters are considering using dog urine as a repellant.(20) An experimental study
demonstrated that dog feces are an effective repellent for sheep, with no habituation observed over
seven successive days.(1)
One Colorado study showed mixed effects of dogs on wildlife.(44) The study compared effects of
pedestrians alone, pedestrians with leashed dogs and unleashed dogs alone on grassland birds. Vesper
Sparrows (Pooecetes gramineus) and Western Meadowlarks (Sturnella neglecta) waited until dogs were
closest to flush that is, they fly or run away. This could be an attempt to remain undetected against the
greatest threat, but could also mean that these bird species perceive humans as a greater threat than
dogs. However, the same study found strong dog-specific impacts on mule deer in woodlands. A
literature review found that ungulates (deer, elk and sheep) had stronger flight responses in open
habitats compared to forested habitats.(63) Unlike small ground-nesting songbirds, larger animals would
have no cover and could easily be seen in open habitats.
The disturbance effects of off-leash dogs are stronger than on-leash and substantially expand the
amount of wildlife habitat affected,(32,59,63,69) and the unpredictability of off-leash dogs may prevent
wildlife habituation in large areas of habitat.(5,10,32,61,69) The negative effects are increased even further
when dogs and people venture off-trail, probably because their behavior is less predictable.(44,67) Off-
leash dogs are likely to reduce the number and types of wildlife in large areas of habitat.
A Colorado study found off-leash dogs ventured up to 85 meters from the trail, although this result was
from 1 square meter plots covering a very small percentage of the area. (33) Remote cameras in another
study documented the same dog 1.5 miles apart in the same day.(61) In Utah, mule deer showed a 96%
probability of flushing within 100 meters of recreationists located off trails; their probability of flushing
did not drop to 70% until the deer were 390 meters from the recreationists.(67) A California shorebird
study found that off-leash dogs were a disproportionate source of disturbance, and that plovers did not
habituate to disturbance; birds were disturbed once every 27 minutes on weekends.(32)
To illustrate the potential of dogs to displace wildlife we explored two well-known local park examples
that allow dogs on leash. Forest Park is one of the largest urban parks in the U.S. and was always
intended to connect urban dwellers with nature; people have been walking their dogs there since before
the park’s 1948 dedication. Forest Park covers 5,172 acres of forest, including approximately 80 miles of
trails and service. Using a very conservative 25-meter buffer around mapped trails to represent the
“human + dog on leash” area of disturbance and assuming 100% compliance with leash rules, the area
affected would be 1,406 acres that’s 28% of the entire park. In 651-acre Tryon Creek Natural Area, 207
acres of land (32%) is within 25 meters of a trail.
Stress response is the functional response of an animal to an external stressor, such as seasonal changes
in temperature and food availability or sudden disturbance.(3) Specific stress hormones are released to
enable the animal to physically respond to the stressor. Acute stress response, when an animal reacts to
an immediate situation, can benefit an animal by triggering it to respond appropriately to a threat.
However, chronic stress such as repeated disturbances over time may reduce wildlife health,
reproduction, growth, impair the immune system and increase vulnerability to parasites and
Dogs cause wildlife to be more alert, which reduces feeding, sleeping, grooming and breeding activities
and wastes vital energy stores that may mean life or death when resources are low, such as during
winter or reproduction.(8,32,40,41,69) Animals release stress hormones and their heart rates elevate in
response.( 3,27,37,38) When stress becomes too high, animals may flush, freeze, or hide.(26,30)
Several studies document that disturbance reduces reproductive success for some wildlife
species.(11,35,40,50,63) Numerous studies found that female deer and elk, and deer and elk groups with
young offspring, show greater flight responses to human disturbances than other groups.(63) Stress
hormones may cause male songbirds to reduce their territorial defense, females to reduce feeding of
their young, nestlings to have reduced weight and poor immune systems, and adult birds to abandon
nests.(11,34,35,76) A Colorado study showed that elk repeatedly approached by humans had fewer young.(50)
Although research is lacking on whether dogs specifically reduce the reproductive success of wildlife, the
fact that humans with dogs create much stronger disturbance effects than without dogs (5,33,38,41,44,61,68,69)
implies that these stress effects would be magnified if people had dogs with them.
Dogs chase and kill many wildlife species including reptiles, small mammals, deer and
foxes.(12,13,29,31,48,58,62) A Canadian study found that domestic dogs were one of the top three predators
that killed white-tailed deer fawns.(4) In northern Idaho winter deer grounds, an Idaho Fish and Game
conservation officer witnessed or received reports of 39 incidents of dogs chasing deer, directly resulting
in the deaths of at least 12 animals.(36) A study in southern Chile revealed that domestic dogs preyed on
most of the mammal species present in the study area.(60) A 2014 literature review of dogs in parks
identified 19 studies that investigated the effects of dogs preying on wildlife.(73) Of these, 13 reported
observing or finding strong evidence of dog predation on wildlife. The Audubon Society of Portland’s
Wildlife Care Center took in 1,681 known “dog-caught” injured animals from 1987 through March
Dogs transmit diseases to wildlife and vice versa including rabies, Giardia, distemper and
parvovirus.(18,23,66,74) A Mexico City study concluded that feral dogs continually transmitted parvovirus,
toxoplasmosis and rabies to wildlife including opossums, ringtails, skunks, weasels and squirrels.(66) Large
carnivores such as cougars are especially vulnerable to domestic dog diseases including canine
Under the Oregon Department of Environmental Quality (DEQ), Metro is a Designated Management
Agency to protect water quality in compliance with the federal Clean Water Act. Limiting dog access at
most natural areas is one of Metro’s commitments to DEQ, because dog feces pollute water. Feces are
often delivered to waterways through stormwater.(57) The average dog produces ½ to ¾ pound of fecal
matter each day a hundred dogs can produce more than 500 pounds of waste per week.(45) The DEQ
identifies pet waste as a significant contributor to one of the region’s most ubiquitous and serious
pollutants, E. coli bacteria. Contact with E. coli-polluted water can make people sick. Because dog waste
can be a relatively simple source to reduce or eliminate exposure to E. coli, DEQ considers reducing or
eliminating dog waste an important action item in jurisdictions clean water implementation plans for
the Willamette Basin watershed.(47)
Humans can catch parasites and diseases such as hookworms (causes rash), roundworms (may cause
vision loss in small children, rash, fever, or cough) and salmonella (causes gastrointestinal illness) from
dog waste.(7,57) Aside from potential illnesses, dog waste can negatively affect visitors’ experience in a
natural area. Dog waste left on the ground is a leading complaint in Portland parks, and violators may be
fined up to $150 per incident.(14)
Several examples illustrate local dog impacts. A Clean Water Services DNA study found that dog waste
alone accounts for an average of 13% of fecal bacteria in stream study sites in the Tualatin River
Basin.(17) Off-leash dog walking is documented to cause erosion in Portland’s Marshall Park, creating
sediment problems in stream water.(15) In 2014 Portland school administrators expressed concern
because playgrounds had become “a minefield for animal waste” from people using school grounds as
after hours, off-leash dog parks, threatening the health of school children.(21) The City of Gresham found
extremely high levels of E. coli bacteria in water quality samples of a very specific stretch of a stream,
where dog feces were found along stream banks behind several yards with dogs.1 The city sent letters to
1 Personal communication with Katie Holzer, Watershed Scientist at the City of Gresham, Oregon, 4/11/2016.
residents in the neighborhood about the incident and how to properly dispose of dog feces; the levels
have not been elevated in follow-up sampling.
People do not always take responsibility for their impacts on wildlife. Several studies demonstrate that
natural area visitors, including dog owners, often don’t believe they are having much of an effect on
wildlife, or assign blame to different user groups rather than accepting responsibility themselves.(6,64,67,68)
Some natural area visitors assume that when they see wildlife, it means that they are not disturbing the
animals or worse, that because they didn’t see any wildlife, they didn’t disturb any.(64)
For example, in Utah, about half of recreational visitors surveyed did not believe that recreation was
having a negative impact on wildlife; of those that did, each user group blamed other groups for the
strongest impacts.(67) In Austria, 56% of people surveyed at a national park agreed that wildlife is in
general disturbed by human activity.(64) However, only 12% believed that they had disturbed wildlife in
their visit that day, and dog-walkers ranked their activities as less disturbing than other user groups’
activities. When asking different user groups to rate the impacts of overall human disturbance on
wildlife, dog-walkers rated the impacts the lowest, at 2.6 out of 5 possible impact points.
Surveys indicate that many dog owners desire fewer restrictions, while non-dog owners often feel the
opposite.(72,73) However dog owners don’t always follow the rules, and some dog owners allow their
dogs to run free in leash-only natural areas.(32,52,73) In a Santa Barbara study, only 21% of dogs were
leashed despite posted leash requirements.(32) And despite regulations and claims to the contrary, dog
owners often don’t pick up their dog’s waste.(6,32) An English study revealed that although 95% of
visitors claimed to pick up their dog’s waste only 19-46% actually did so, depending on location within
the park.(6)
In summary, people and their dogs disturb wildlife, and people are not always aware of or willing to
acknowledge the significance of their own impacts. Wildlife perceive dogs as predators. Dogs subject
wildlife to physical and temporal displacement from habitat, and dog scent repels wildlife with lingering
impacts. Dogs disturb wildlife which can induce long-term stress, impact animals’ immune system and
reduce reproduction. Dogs spread disease to and outright kill wildlife. People with dogs are much more
detrimental to wildlife than people alone; off-leash dogs are worse; and off-trail impacts are the highest
(Figure 1).
Urban wildlife is subjected to many human-induced stressors including habitat loss, degraded and
fragmented habitat, impacts from a variety of user groups, roads, trails, infrastructure, noise and light
pollution.(26) These stressors will increase with population; from July 2014 to 2015 the Portland-
Vancouver metropolitan region added 40,621 new residents.(43) Current population in the region stands
at 2.4 million, with another 400,000 residents expected over the next 20 years.
Figure 1. Conceptual illustration of the relative impacts on
wildlife due to people without and with dogs.
Among medium to high density cities, Portland currently ranks second in the total area covered by parks
at nearly 18%, and also second in the number of park acres per resident.(25) Of 34 park providers in the
Portland region, all but four allow dogs in most or all of their natural areas, typically on-leash; more than
two-thirds also offer dog parks or off-leash dog areas (Table 1 at end of document).
Wildlife conservation is not the only valid reason to preserve natural areas. Park providers must weigh
the trade-offs between wildlife, habitat, water quality and recreational values. But when considering
different types of public access in a natural area, it is important to understand that the research is clear:
people with dogs substantially increase the amount of wildlife habitat affected and are more
detrimental to wildlife than people without dogs.
No people
People on
People on
trail, dogs on
People on
trail, dogs
People off
trail, dogs
People off
trail, dogs
Disturbance Level
Items in bold are from peer-reviewed journals
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birds. Journal of Environmental Management 92:2287-2294.
66. Suzan G, Ceballos G. 2005. The role of feral mammals on wildlife infectious disease prevalence in
two nature reserves within Mexico City limits. Journal of Zoo and Wildlife Medicine 36:479-484.
67. Taylor AR, Knight RL. 2003. Wildlife responses to recreation and associated visitor perceptions.
Ecological Applications 13:951-963.
68. Taylor K, Taylor R, Anderson P, Longden K, Fisher P. 2005. Dogs, access and nature conservation.
English Nature Research Report 649, 1-2.
69. Thomas K, Kvitek RG, Bretz C. 2003. Effects of human activity on the foraging behavior of
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70. Thompson MJ, Henderson RE. 1998. Elk habituation as a credibility challenge for wildlife
professionals. Wildlife Society Bulletin 26:477-483.
71. UK CEED. 2000. A review of the effects of recreational interactions within UK European marine sites.
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72. Webley P, Siviter C. 2006. Why do some owners allow their dogs to foul the pavement? The social
psychology of a minor rule infraction. Journal of Applied Social Psychology 30:1371-1380.
73. Weston MA, Fitzsimons JA, Wescott G, Miller KK, Ekanayake KB, Schneider T. 2014. Bark in the
park: A review of domestic dogs in parks. Environmental Management 54:373-382.
74. Whiteman CW, Matushima ER, Cavalcanti-Confalonieri UE, Palha MDDC, Da Silva ADSL, Monteiro
VC. 2009. Human and domestic animal populations as a potential threat to wild carnivore
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Table 1. Park providers’ dog policies in the greater Portland, Oregon metropolitan area.
Parks provider
No dogs
allow dogs
Free to
areas or
dog park
Audubon Society of Portland
City of Beaverton
City of Cornelius
City of Durham
City of Fairview
City of Forest Grove
City of Gladstone
City of Gresham
City of Happy Valley
City of Hillsboro
City of Lake Oswego
City of Milwaukie6
City of Oregon City
City of Portland
City of Sherwood
City of Tigard
City of Troutdale
City of Tualatin
City of West Linn
City of Wilsonville
City of Wood Village
Clackamas County
Clean Water Services (Fernhill
2 All parks except fountain provided by Tualatin Hills Parks & Recreation District.
3 Considering off-leash dog area at Water Park.
4 Dogs on leash allowed at all parks except Salish Ponds (no dogs).
5 Dogs on leash except prohibited in playgrounds.
6 All city parks are operated by North Clackamas Parks and Recreation Department.
7 The City of Oregon City is currently testing off-leash areas in three parks.
8 Dogs on-leash except prohibited at Foster Floodplain Natural Area, Tanner Springs Park, Whitaker Ponds Nature
Park, Riverview Natural Area, and the amphitheater at Mt Tabor Park.
9 33 off-leash dog areas.46
10 Most parks: dogs not allowed. Exception: Sunrise Park and large Beaver Creek Greenway, leash only. Considering
two more on-leash dogs allowed parks.
11 Plans for an off-leash area at Sunrise Park.
12 One off-leash dog area: field near parking lot at Mary S. Young Park. Off-leash dogs were identified as an issue by
parks board.
Parks provider
No dogs
allow dogs
Free to
areas or
dog park
Federal / State (Sandy River Natural
N. Clackamas Parks & Recreation
OR Department of Fish and Wildlife
OR Parks & Recreation Department
Port of Portland
The Nature Conservancy
The Wetlands Conservancy
Tualatin Hills Park and Rec. District
U.S. Fish & Wildlife Service
U.S. Forest Service19
13 Leashes required only on/near Confluence Trail and in parking area. Leash-off everywhere else. Region’s largest
off-leash area, and heavily used.
14 Metro does not allow dogs except for service dogs, leashed dogs on regional trails, Broughton Beach, boat ramps
and properties managed by others through intergovernmental agreements that are integrated into larger parks
where leashed dogs are allowed (e.g., Forest Park).
15 All dogs must be on leash, except while hunting during seasons authorized on Sauvie Island Wildlife Area, or
pursuant to a valid “Competitive Hunting Dog Trial Permit” or “Sauvie Island Wildlife Area Individual Dog Training
16 Includes Vanport Wetlands and mitigation sites. No dogs allowed except Government Island State Recreation
Area (leased to Oregon Parks Department).
17 No formal policy.
18 Dogs allowed on-leash except Tualatin Hills Nature Park and Cooper Mountain Nature Park.
19 Refers specifically to the Sandy River Delta, owned and administered by the National Forest Service, Columbia
River Gorge National Scenic Area.
... One exception to this pattern was documented in grassland birds in Argentina where four out of five species were alert to tangential approaches at greater distances than to direct approaches (Fernández-Juricic et al. 2005). Grassland birds may have a different antipredator response than forest birds, preferring to hide rather than flush when approached directly (Hennings 2016). This is supported by a study in Colorado, which found that grassland birds responded most strongly to dogs, with or without a human present (Miller et al. 2001). ...
... One hypothesis regarding the somewhat counterintuitive but comparatively strong response to an approach on foot is that a person on foot may resemble a predator more than a person on horseback or in a vehicle. Last, the presence of dogs has been found to elicit very strong responses from many species (Hennings 2016). ...
... However, common grassland and forest birds might not have strong responses to dogs (Miller et al. 2001). The effects of dogs on wildlife have also been reviewed extensively (see Hennings 2016). ...
... We previously reviewed the literature pertaining to the effects of dogs on wildlife (Appendix 1). [287] The evidence that dogs negatively affect wildlife is found repeatedly throughout the literature. People with dogs -on leash and even more so for off-leash dogs -appear to be more detrimental to wildlife than people without dogs. ...
... We suggest the possibility that grassland birds react differently to predators compared to forest-dwelling birds due to their visibility upon flushing in open structure habitats; in some cases it may be safer to hide than to flush. Miller et al.'s study in Colorado grasslands supports this theory; dogs consistently elicited the strongest anti-predator response (Appendix 1), [287] yet grassland birds had shorter FIDs when approached by a human with a dog or a dog alone, compared to a human without a dog. [322] The next section addresses relationships between vegetation cover and antipredator response in more detail. ...
... Our previous review on the effects of dogs on wildlife revealed a pattern in which humans with dogs were more disturbing to wildlife than humans without dogs (Appendix 1). [287] SMALLER MAMMALS We found only a few trail-related studies on smaller non-carnivorous mammals. In Wyoming, the abundance of red squirrels subjected to low levels of disturbance (1-5 human disturbance events per week) did not differ from controls, although higher disturbance levels may have revealed effects. ...
Technical Report
Full-text available
Metro is the regional government in the Portland, Oregon area. Thanks to the region’s voters, the agency has acquired approximately 17,000 acres of natural areas to protect water quality, wildlife habitat and connect people with nature. The goal of this document is to better understand the trade-offs between different types and levels of recreational access in the context of our work to protect habitat and water quality, and provide access to nature in a growing urban area. Only by thoroughly understanding the effects of recreational activities on wildlife and water quality are we able to avoid, minimize and mitigate potential harm to the resources we are committed to protecting. Recreation ecology is the scientific study of environmental impacts resulting from recreational activity in protected natural areas. The nature of a literature review is to summarize what has been studied, what has been learned, and what the experts have concluded. This document reviews the literature on overall and relative effects of three user groups – hikers, mountain bikers and equestrians – on trails, habitat, and wildlife to help inform ecologically appropriate placement and construction of trails in natural areas. Studies are reviewed from the U.S. and elsewhere, with a focus on soft-surface trails in natural areas. We included limited information about other non-motorized trail user groups such as trail runners and beach walkers. Motorized off-road vehicles were omitted from this review because they are generally not allowed on natural area trails within the urban and near-urban region. A previous literature review on the effects of dogs on wildlife and water quality is included as Appendix 1. Studies vary in terminology for our recreational groups of interest. In this report “hiker” generally means a person walking along a trail for various reasons such as exercise, wildlife watching or moving between places. “Mountain biker” refers to a non-motorized bicycle rider on a soft or natural surface trail; alternative terms in the literature include off-road bicyclists or off-road cyclists. “Equestrian” refers to a person riding a horse on a trail. Throughout the text we refer to these as “user groups.” Trails provide people with important opportunities to improve health and well-being, and providing access to nature is especially important in urban areas.[2-5] However, as indicated in various literature reviews, trails and trail use can damage natural areas including negatively affecting soils, vegetation, water quality, plants, and animals.[6-27] Damage to trails or habitats and negative effects on wildlife are more likely when trails are inappropriately located, designed, constructed, maintained or used, or when unauthorized trails are allowed to proliferate. These issues can also increase trail maintenance costs[28-30] and negatively affect visitors’ experience.[31-33] This document reviews the types of recreational effects in Chapters 2-7, including information about user group-specific effects. Each chapter includes a summary of key points. Chapter 8 offers information on how to minimize, monitor and manage effects. Throughout the review we provide representative study examples with additional citations. We paid close attention to the effects of recreation on wildlife (Chapters 6 and 7) because they are less well documented than physical effects such as erosion or vegetation damage. Scientific names for species mentioned in the text are in Appendix 2. For wildlife, human disturbance increases animals’ stress and can cause them to hide, change behavior or flee. Some species, such as those that do well in urban areas, are generalists and can tolerate human disturbance. Other species such as pregnant animals, long-distance migrants, and habitat specialists tend to be more stressed and displaced by trail users. Some species may permanently leave a natural area. Figure 1 illustrates the relationships between environmental, trail design, recreational use and their effects on trail damage, water quality, vegetation damage and wildlife...
... Beaver and hu-man observations are significantly negative correlated, indicating that beaver avoid using the area when humans and dogs are present. The negative impact of dogs on wildlife is well documented, including for beaver (Hennings 2016;Schüttler et al. 2018). The Place dike, which sits between the lodge area and the west Elwha River riparian and side channel areas, is the sole recreation access to the west delta and used heavily used for recreation, including heavy domestic dog use. ...
Full-text available
In this paper we assess long-term trends and habitat changes to understand the relationships between coastal beaver (Castor canadensis), salmon, shoreline alterations, large-scale dam removals and nearshore ecological restoration. From this work we conclude that the removal of two large scale dams in the Elwha River has benefited beaver use of the coastal zone through water quality changes that allow beaver to re-establish high-quality zones and the expansion of riparian zones that provide extensive new food resources to beaver. However, the lower river hydrodynamic processes continue to be disrupted by a 200-meter earthen dike installed by local government and landowners for flood protection in the Elwha coastal zone in the 1960's. The dike acts as a driver of lower river geomorphology and has resulted in the formation of a large and persistent lateral bar along the lower river channel. Associated disrupted hydrodynamics are causing a critical coastal zone of the unimpounded lower river side channels to fill in. This channel habitat has decreased by 23%, with an annual average shrinkage rate of 13%, from pre-dam removal size, resulting in a decrease in both quality and quantity of nursery function for juvenile wild fish in a coastal zone that was historically documented to be the highest functioning for endangered juvenile salmon and trout. Inversely, physical changes including improved water quality in the adjacent impounded west side channel and continued expansion of riparian vegetation along the west delta lateral bar ben-efitted coastal beaver that recolonized the west delta after dam removals. The newly colonized coastal beaver may provide ecological engineering services to offset side channel loss as well as promote continued fish access. However recreational use was found to negatively impact beaver use of the area. We therefore recommend a series of additional ecosystem restoration actions that incorporate beaver as an ecosystem restoration component of the coastal zone. These actions include a public outreach program to encourage passive recreation measures to prevent negative impacts to beaver, and legacy, ecosystem scale restoration projects that reconnect the hydrodynamics of the west delta to complete Elwha ecosystem restoration. Together, these steps, if implemented , will result in a synergistic ecosystem restoration throughout the watershed to the benefit of the coastal ecosystem, including both beaver and salmon, as intended by the large-scale dam removal project. Academic editor: Mathias Scholz
Full-text available
Human leisure activities are becoming more and more various and widespread, which may increase their potential consequences for wildlife in terms of disturbance. This paper summarizes existing knowledge on the effect of non-consumptive (i.e. not hunting nor fishing) leisure activities on wildlife. The aim is not to provide an exhaustive literature review but through the selection of relevant literature to examine the various aspects of the subject. First, we present the different definitions of disturbance, list the types of activities most likely to affect wildlife, and the species or taxonomic groups generally considered as being the most susceptible. Then, we summarize the various means of measuring the effects of disturbance, highlighting the fact that, though generally most obvious, changes in animal behaviour are not necessarily the most appropriate index of disturbance. Then we present the various scales at which disturbance has been studied, from individual behaviour to population dynamics. Finally, we suggest further research priorities, especially the recognized need for more experimental studies and studies of long-term effects of disturbance on individual fitness, hence population dynamics, since it is at this scale that appropriate management measures of disturbance have to be taken in the future.
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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.
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Sex hormones, reproductive status, and pathogen load all affect stress. Together with stress, these factors can modulate the immune system and affect disease incidence. Thus, it is important to concurrently measure these factors, along with their seasonal fluctuations, to better understand their complex interactions. Using steroid hormone metabolites from fecal samples, we examined seasonal correlations among zebra and springbok stress, reproduction , gastrointestinal (GI) parasite infections, and anthrax infection signatures in zebra and springbok in Etosha National Park (ENP), Namibia, and found strong seasonal effects. Infection intensities of all three GI macroparasites examined (strongyle helminths, Strongyloides helminths, and Eimeria coccidia) were highest in the wet season, concurrent with the timing of anthrax outbreaks. Parasites also declined with increased acquired immune responses. We found hormonal evidence that both mares and ewes are overwhelmingly seasonal breeders in ENP, and that reproductive hormones are correlated with immunosuppression and higher susceptibility to GI parasite infections. Stress hormones largely peak in the dry season, particularly in zebra, when parasite infection intensities are lowest, and are most strongly correlated with host mid-gestation rather than with parasite infection intensity. Given the evidence that GI parasites can cause host pathology, immuno-modulation, and immunosuppression, their persistence in ENP hosts without inducing chronic stress responses supports the hypothesis that hosts are tolerant of their parasites. Such tolerance would help to explain the ubiquity of these organisms in ENP herbivores, even in the face of their potential immunomodulatory trade-offs with anti-anthrax immunity.
Wildlife populations are under increasing pressure from a variety of threatening processes, ranging from climate change to habitat loss that can incite a physiological stress response. The stress response influences immune function with potential consequences for patterns of infection and transmission of disease among and between wildlife, domesticated animals and humans. This is concerning because stress may exacerbate the impact of disease on species vulnerable to extinction with consequences for biodiversity conservation globally. Furthermore, stress may shape the role of wildlife in the spread of Emerging Infectious Diseases (EID) such as Hendra virus (HeV) and Ebola. However, we still have a limited understanding of the influence of physiological stress on infectious disease in wildlife. We highlight key reasons why increased attention to the relationship between stress and wildlife disease could benefit conservation, animal and public health and discuss approaches for future investigation. In particular, we recommend increased attention be given to the influence of anthropogenic stressors including climate change, habitat loss and management interventions on disease dynamics in wildlife populations.
We offer our perspectives on challenges facing the wildlife profession if habituation behavior becomes prevalent in North American elk (Cervus elaphus). We find it increasingly difficult to ignore habituation in our work with elk and the public in western Montana. The scientific literature documents elk avoidance responses to human activities, but does not provide information to managers that would reconcile apparent contradictions we observe of elk habituation responses in urban fringe areas. Conversations with elk managers and researchers across western North America suggest that elk habituation is a management issue of emerging importance as elk and human populations expand. We examine habituation as an adaptive behavioral strategy for maximizing reproductive fitness and predict that habituated elk populations will be common across the Rocky Mountain west in the 21(st) century. To reduce habituation risk, managers should consider options that may differ radically from traditional elk management strategies (i.e., to protect elk habitat). We challenge researchers to describe relationships between increasing levels of habituation in elk and environmental factors within management control.
Responses of Rocky Mountain National Park elk (Cervus canadensis) to human activities were quantified in autumn 1974 and winter-spring 1975. During autumn, numbers of elk seen, rates of bugling, times of arrival and departure of elk to and from meadows, and harem bulls' activities were analyzed for relationships with traffic volume and tourist activities. Results suggested small effects of traffic volume upon elk, but no trends were statistically significant. People approaching animals off roads usually caused elk to leave open areas. Harassing elk in 2 meadows on alternate weeks during winter and spring did not affect their distribution or observability on winter ranges. Elk made greater use of areas near roads as the winter-spring study progressed, suggesting slight avoidance of roads when forage was more abundant earlier in winter. Wintering elk often used a residential area at night when human encounters were minimal. During winter and spring, elk were approached significantly closer during darkness with artificial lights than during daylight. These elk, which experienced little or no hunting, were very visible and were disturbed little, if any, by normal on-road visitor activities.
Consumption of food by Aplodontia rufa from bowls scented with control odors, secretion from anal glands of minks (Mustela vison), or urine from minks, bobcats (Felis rufus), and coyotes (Canis latrans) was studied. In two-choice control tests, subjects indiscriminately consumed apple from unscented bowls and from bowls scented with urine from an unfamiliar herbivore (Cavia porcellus), or with butyric acid. During two-choice tests offering apple from bowls scented with secretion from anal glands of minks and from bowls scented with butyric acid, significantly less apple was consumed from bowls containing mink scent. In two-choice tests in which apple was offered from bowls scented with urine from either mink, bobcat, coyote, or domestic dog, all predator urines reduced feeding. Habituation was studied by measuring consumption of dry pellets during continuous exposure to coyote urine for 5 days. Significantly less chow was consumed from bowls scented with coyote urine than from control bowls, indicating a lack of habituation to the predator scent. We conclude that predator scents act as natural repellents. The responsiveness to scents from several sympatric predators as well as from domestic dogs suggest an innate reaction to a signal, which is common to carnivores. The utility of predator scents in the control of browsing damage by mountain beavers should be explored.