{"id":2178660,"date":"2024-11-21T06:00:16","date_gmt":"2024-11-21T05:00:16","guid":{"rendered":"https:\/\/focusingonwildlife.com\/news\/?p=2178660"},"modified":"2024-11-17T08:21:11","modified_gmt":"2024-11-17T07:21:11","slug":"bobcats-are-back-and-theyre-helping-protect-people-from-zoonotic-disease","status":"publish","type":"post","link":"https:\/\/focusingonwildlife.com\/news\/bobcats-are-back-and-theyre-helping-protect-people-from-zoonotic-disease\/","title":{"rendered":"Bobcats are back, and they\u2019re helping protect people from zoonotic disease"},"content":{"rendered":"

A bobcat, with its characteristic reddish fur and black markings, trots across a snow-covered field in central Oregon, in the U.S. Pacific Northwest, hunting birds at the Warm Springs National Fish Hatchery. It could almost be mistaken for a giant domestic cat, except for its massive legs, a shorter neck than any house feline, ears topped with thin tufts of dark fur, and a stubby tail standing up straight. Though seldom seen by people, Lynx rufus is the most successful small wildcat in North America.<\/p>\n

\u201cBobcats are in the process of a large-scale recovery and have an almost continental distribution, in the United States, at least \u2014 from the West to the East, and North to South,\u201d said Taal Levi, a biologist at Oregon State University who studies the effects of hunting, disease and climate change on wildlife.<\/p>\n

Bobcat numbers were nearly nil by around 1900, but have rebounded to several million today, ranging from southern Canada through the contiguous United States into southern Mexico.<\/p>\n

They\u2019re resilient, even when living at the edge of asphalt and near people. Bobcats remain wild and elusive while hunting and residing near towns. Security cameras often catch them skulking down roads and up driveways, sometimes rummaging in people\u2019s gardens, chasing a rabbit, or tossing around a mouse snatched from beneath a foundation. Bobcats also use human-built hiking trails \u2014 or, perhaps, it\u2019s humans who made trails along the bobcats\u2019 forested routes.<\/p>\n

\u201cI often saw them hunting on the trails I ran [near San Francisco, and] running in front of me on trails. Their presence was a reminder of the wildness that still exists in our urban spaces,\u201d says Zara McDonald, who founded the Felidae Conservation Fund to study and reduce threats to large cats living on the urban fringe. The fund\u2019s new Bay Area Bobcat Project monitors \u201cthe health and movement of bobcats in urban-edge habitats and studies the impacts of human activity on their populations,\u201d McDonald told Mongabay in an email.<\/p>\n

Strong as its numbers may be today, the species faces many human-caused dangers: from the built environment, road traffic, and widely used rodent poisons. Yet we continue benefiting from the strong presence of these stealthy small cats in our ecosystems. Their being here lowers the risk of zoonotic disease (those passed from animals to humans), partly because bobcats are poor reservoirs for known diseases, and also because they help control mice, a major disease vector.<\/p>\n

Status good but facing many risks<\/h2>\n

Bobcats are listed as a species of least concern on the IUCN Red List of Threatened Species. The IUCN, the global wildlife conservation authority, reports that development, the fur trade, rodent poison, and habitat loss hindering the species\u2019 movement safely throughout its range all threaten bobcat survival.<\/p>\n

Canine distemper has affected bobcats in eastern Canada, and conflicts with domestic and feral dogs in northern Mexico also threaten the wildcat. Hybridization between bobcats and Canadian lynx (Lynx canadensis) may require \u201cconservation actions for the endangered lynx recovery,\u201d according to the IUCN.<\/p>\n

Florida is the only U.S. state where bobcats are reported declining. There, exotic and invasive Burmese pythons (Python bivittatus) eat the same small mammals that the wildcats hunt. In California, bobcats are estimated to number 70,000 to 100,000. The population is doing so well there, in fact, that state officials are considering whether to reinstate bobcat hunting in 2025 after a five-year ban. Hunting L. rufus is legal in most of the rest of the United States.<\/p>\n

\u201cHere in the East Coast of the U.S., they are one of our larger mammals,\u201d said Felicia Keesing, a biologist and researcher at Bard College in New York state, whose 2021 study, carried out along with Richard Ostfeld of the Cary Institute of Ecosystem Studies, found that biodiversity loss increases the risk of human exposure to known and new zoonotic pathogens.<\/p>\n

Bobcats are predators, Keesing noted, so \u201care more sensitive to biodiversity loss. They need a big area\u201d to roam. Yes, bobcats may wander through towns and subdivisions, she added, but that isn\u2019t optimal behavior, and these wildcats need more in terms of habitat: \u201cA bobcat needs a big area of forest to survive. It\u2019s not that they won\u2019t ever leave that forest and wander into someone\u2019s yard. But they don\u2019t just need a yard. They need the forest.\u201d<\/p>\n

\"A
A bobcat at Sonny Bono Salton Sea National Wildlife Refuge, near agricultural lands of California\u2019s Imperial Valley and on the border of the Sonoran Desert ecosystem. Image courtesy of Mark Stewart\/U.S. Fish and Wildlife Service.<\/figcaption><\/figure>\n

To thrive in urban northern California, bobcats must be able to move from wild mountain range to mountain range without being blocked by the human civilization found in the valleys between. Laurel E.K. Serieys led a 2021 bobcat study conducted by researchers from the University of California, Santa Cruz, and the University of Cape Town in South Africa. For 131 days, the team tracked the movements of 36 bobcats they had trapped, radio-collared and released to see how they moved along two narrow, fragmented, partially developed corridors, moving from California\u2019s Coyote Valley to the Aromas Hills \u2014 a distance of about 60 kilometers (40 miles).<\/p>\n

These particular natural corridors are known as the \u201clast chance\u201d routes for wildlife moving between the Santa Cruz Mountains and the Diablo and Gabilan ranges. Corridors like this one are vital for genetic mixing and maintaining species resilience.<\/p>\n

However, the researchers found that traveling these routes can be dangerous. Most of the bobcats found dead in the area (some collared and some not) had been hit by vehicles or died of disease. \u201cOur findings have driven conservation action through land acquisition,\u201d the researchers wrote.<\/p>\n

The northern California bobcat study also determined that 94% of those found dead had been exposed to rat poison, probably by eating small mammals that had eaten the poison. These toxins are anticoagulants that kill rodents by preventing blood clotting, which makes them bleed to death. For a decade, California has limited the use and, since 2020, the sale of the most common of such poisons. In January 2024, diphacinone, the most widely used poison, was banned for most uses.<\/p>\n

Past research documented a similar mortality pattern. A 2018 study led by Devaughn Fraser of the University of California found that anticoagulant rodenticides hurt the health of bobcats that eat poisoned dead rodents. A 2007 study of bobcats and mountain lions in Southern California found more than 90% tested positive for the same poisons.<\/p>\n

\"Two
Two bobcats perch atop a tree at Maxwell National Wildlife Refuge, Kansas. Image courtesy of Chris Moehring\/U.S. Fish and Wildlife Service.<\/figcaption><\/figure>\n

Helping reduce zoonotic disease<\/h2>\n

Humanity has good reason to want to conserve bobcats and other large mammals. Large animals in an ecosystem reduce the spread of disease-causing organisms that can pass from wild animals to humans, a mechanism known as the dilution effect.<\/p>\n

Much of the research on the dilution effect has focused on Lyme disease, which is caused by a bacterium prevalent in the U.S. Northeast. Blacklegged ticks (Ixodes scapularis) feed on Lyme disease-infected animals and can pass Lyme to humans when they bite and attach to them.<\/p>\n

Like many mammals, bobcats also carry Lyme disease, yet are poor at passing along the Borrelia burgdorferi bacteria that causes the disease. In fact, ticks that feed on infected bobcats rarely transmit the Lyme bacteria to the next mammal they bite. The most efficient hosts and vector of Lyme are white-footed mice (Peromyscus leucopus), which almost always do pass on the bacteria to ticks that bite them.<\/p>\n

Bobcats feed heavily on the mice, so reduce their populations. In a 2016 study, Keesing, Levi, Ostfeld and others modeled the dilution effect throughout the ticks\u2019 life cycle. Among the researchers\u2019 conclusions: Bobcats, coyotes and other larger mammals \u201cmay reduce the density of small mammals\u201d like mice which are efficient hosts for zoonotic diseases.<\/p>\n

\u201cIf a tick feeds on a white-footed mouse, it is almost certain to pick up the bacterium,\u201d Keesing said in an interview. But \u201cIf it feeds on a bobcat, it is almost certainly not going to pick up the bacterium. It\u2019s not that they [bobcats] don\u2019t get infected, it is that they don\u2019t pass on the bacterium.\u201d<\/p>\n

But when large mammals are removed from an ecosystem and biodiversity becomes low, the environment is degraded and \u201cmice are the only thing left,\u201d she added. \u201cThe ticks feed on them. And all, or [about] 92% of the ticks become infected. That happens because the other [wildlife] they feed on are not there.\u201d<\/p>\n

\"Bobcat
Bobcat walking along electrical wires at the Kennedy Space Center, Florida. These small wildcats frequently move and hunt within rural and suburban human communities, though they need forest habitat to truly thrive. Image by NASA via Wikimedia Commons (Public domain).<\/figcaption><\/figure>\n
\"Bobcat
Bobcat 332, a male photographed in the Simi Hills near Santa Monica, California, had severe mange, a skin disease caused by mites. Blood samples showed it also had rat poison in its body. Image courtesy of the National Park Service.<\/figcaption><\/figure>\n

Not only do mice help ticks survive, Keesing added, in a degraded ecosystem without their predators, mice numbers can explode. \u201cWhen bobcats and foxes aren\u2019t there, then mice are free to become abundant.\u201d<\/p>\n

Scientists continue trying to understand the precise roles each animal plays in an ecosystem in relation to disease. In a healthy habitat, \u201cIf the tick would have otherwise fed on a mouse, now it feeds on some other [large] host\u201d which is poor at transmitting disease, Levi said. So the presence of big predators \u201creduces infection prevalence.\u201d<\/p>\n

But there\u2019s a hitch: ticks can thrive whether what they bite helps spread disease or not, Levi added, and they can still potentially spread disease later on, by feeding on mice and then humans. \u201cThe initial ideas around the dilution effect focused on diverting blood meals away from mice,\u201d Levi said. \u201cBut some of those blood meals go to ticks that otherwise wouldn\u2019t have fed at all, [so] the population of ticks can increase.\u201d<\/p>\n

This suggests that even in a diverse ecosystem full of mammals like bobcats that are poor disease hosts, lots of ticks could still amplify Lyme disease. That is because ticks thrive over their two-year lifespans by biting different animals at the larval, nymph and adult stages.<\/p>\n

\u201cTrying to disentangle those [relationships] is quite challenging,\u201d Levi said. \u201cWe don\u2019t have a good model for tick demography \u2014 like what limits population growth.\u201d<\/p>\n

\"Sometimes
Sometimes homeowners catch glimpses of bobcats, and are lucky enough to grab photos of them. This bobcat carries a squirrel it\u2019s hunted near two houses above the Connecticut River in Chester, Connecticut. Image courtesy of Priscilla Martel.<\/figcaption><\/figure>\n

California ban on bobcat hunting could be lifted<\/h2>\n

Humans continue to influence bobcat numbers. Four years ago, for example, California halted bobcat hunting, pending the results of population and health surveys by the state\u2019s Department of Fish and Wildlife. Commercial trapping was banned earlier, all of which helped numbers rise.<\/p>\n

State scientists spent two years collecting data at 48 study sites, tracking collared bobcats across a dozen counties. They took 21 million photos, collected 3,000 scat samples, and analyzed DNA. The results, and a decision on whether hunting can begin again, are expected in early 2025.<\/p>\n

McDonald of the Felidae Fund said the state had shown the NGO \u201caspects of their management plan \u2026 and we are concerned about the lack of robust data being used to justify a reinstatement of hunting.\u201d She underlined the importance of bobcats to ecological well-being, noting that the species is \u201can integral part of the food chain, controlling prey populations and maintaining the balance in ecosystems.\u201d<\/p>\n

Levi agreed, noting that while \u201cThe populations are as strong as they\u2019ve been in a century, the public does not appreciate the degree to which we [have] had an ongoing recovery of pumas [Puma concolor] and bobcats.\u201d Nor are most people aware of how these booming wildcat populations are helping protect communities from Lyme and other zoonotic diseases.<\/p>\n

\"A
A quick glance at this bobcat might cause a passerby to mistake it for a really big domestic cat. This particular bobcat was spotted and photographed in Wichita Mountains National Wildlife Refuge, Oklahoma. Image courtesy of Steve Enter\/U.S. Fish and Wildlife Service.<\/figcaption><\/figure>\n

Citations:<\/h2>\n

Keesing, F., & Ostfeld, R. S. (2021). Impacts of biodiversity and biodiversity loss on zoonotic diseases. Proceedings of the National Academy of Sciences, 118(17). doi:10.1073\/pnas.2023540118<\/p>\n

Serieys, L. E. K., Rogan, M. S., Matsushima, S. S., & Wilmers, C. C. (2021). Road-crossings, vegetative cover, land use and poisons interact to influence corridor effectiveness. Biological Conservation, 253, 108930. doi:10.1016\/j.biocon.2020.108930<\/p>\n

Fraser, D., Mouton, A., Serieys, L. E. K., Cole, S., Carver, S., Vandewoude, S., \u2026 Wayne, R. (2018). Genome\u2010wide expression reveals multiple systemic effects associated with detection of anticoagulant poisons in bobcats (Lynx rufus). Molecular Ecology, 27(5), 1170-1187. doi:10.1111\/mec.14531<\/p>\n

Riley, S. P. D., Bromley, C., Poppenga, R. H., Uzal, F. A., Whited, L., & Sauvajot, R. M. (2007). Anticoagulant exposure and notoedric mange in bobcats and mountain lions in urban Southern California. The Journal of Wildlife Management, 71(6), 1874-1884. doi:10.2193\/2005-615<\/p>\n

Levi, T., Keesing, F., Holt, R. D., Barfield, M., & Ostfeld, R. S. (2016). Quantifying dilution and amplification in a community of hosts for tick\u2010borne pathogens. Ecological Applications, 26(2), 484-498. doi:10.1890\/15-0122<\/p>\n

This article<\/a> by Christine Woodside was first published by Mongabay.com on 12 November 2024. Lead Image:\u00a0A bobcat navigates a snow-covered branch along the Madison River in Yellowstone National Park. Image courtesy of Neal Herbert\/National Park Service.<\/em><\/p>\n

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