Dear EarthTalk: What is the status of the hyena in the wild? Though unloved by
"The striped hyena and the brown hyena
many, the hyena has always struck me as one of God’s survivors. -- Jim Reddoch, Portland, TX
Among the most intelligent animals on Earth, three species of hyenas still roam in wilder parts of Africa and Asia. Of them, the striped hyena and the brown hyena are most at risk. Both are considered “Near Threatened” by the International Union for the Conservation of Nature (IUCN), which maintains a “Red List” of at-risk and extinct species around the world. The spotted hyena is doing well enough to be considered of “Least Concern” by IUCN, but its population is also declining, primarily due to habitat loss.
In general, hyenas are large, strong, flesh-eating animals that hunt a wide range of prey but mostly feed on carrion (the kills of other predators). They most closely resemble dogs but are in fact more closely related to cats. When full-grown, hyenas range from about 3 1/2 to 5 1/2 feet long and weigh between 75 and 175 pounds. Considered as smart as some primates, hyenas work in teams to hunt zebras and wildebeests. They communicate through a series of yells and growls, and their cries resemble human laughter.
The striped hyena roams a very large, patchy range stretching from northern Africa through the Middle East to India. Biologists estimate that only 5,000 to 14,000 individuals exist today in the wild. According to the IUCN, major reasons for the animals’ decline include persecution (especially poisoning) by humans, decreasing sources of carrion due to declines in the populations of other large carnivores (wolves, cheetahs, leopards, lions and tigers) and their prey, and changes in livestock practices. “Humans are consistently indicated as the major source of mortality…largely because the [hyena] is loathed as a grave robber, and because of incidents of damage to agriculture…and livestock,” reports the IUCN. Also taking a toll is illegal hunting for striped hyena skins and body parts for use in traditional medicine.
Meanwhile, only 5,000 to 8,000 Brown hyenas today roam parts of sub-Saharan Africa. The brown hyena is relatively safe in protected areas, but clashes with humans elsewhere have taken their toll. The IUCN reports that negative attitudes toward brown hyenas prevail across South Africa and elsewhere, with many ranchers and farmers shooting, poisoning, trapping and hunting them with dogs. The UK-based Predator Conservation Trust has established the Brown Hyena Research Project to help form strategies to promote the long-term survival of the species and its southern Africa habitat.
As many as 47,000 spotted hyenas live in sub-Saharan Africa. They suffer similar forms of persecution as other hyenas but have fared better due to their ability to adapt to life in proximity to humans.
The IUCN’s Hyena Specialist Group focuses on developing hyena conservation strategies worldwide through integrated research and public education to change attitudes toward these much maligned animals. Conservationists underscore the importance of preserving hyenas because, if for no other reason, we can learn much from them. For one, hyenas possess unique immune systems that allow them to withstand diseases that kill other animals. “Only if hyenas are available to study will we be able to unravel the mysteries of their immune responses,” reports IUCN.
CONTACTS: International Union for the Conservation of Nature, iucn.org; Predator Conservation Trust, predatorconservation.com; IUCN Hyaena Specialist Group, www.hyaenidae.org.
Dear EarthTalk: I ride my bike to work along busy urban streets. Should I be
|Aside from the obvious
physical safety consider-
ations (especially when
talking on a cell phone!),
biking on highly trafficked
roads exposes riders to
considerable amounts of
fine particles, nitrogen dioxide
and volatile organic compounds
spewing out of tailpipes.
Courtesy of Getty Images
worried about inhaling pollutants from vehicle emissions and other sources? -- J. Kaufman, San Francisco, CA
The short answer is, yes, probably. Cars, trucks and buses emit considerable amounts of airborne pollution as they make their ways along city streets and highways. The fine particles, nitrogen dioxide and volatile organic compounds (VOCs) spewing out of tailpipes have been linked to a wide range of human health problems, from headaches to respiratory illness to cancer. Though Australian researchers found that exposure to these pollutants is actually higher while riding inside a vehicle than while riding a bike, turning your handlebars in the direction of back roads might still be a good idea, for safety’s sake as well.
Western Washington University Geophysicist Bernie Housen, concerned about the air quality on his own bicycle commute along busy Bellingham roads, recently launched a study of the magnetism in local trees to gauge air quality along his route and elsewhere in his region. The magnetism in a tree’s leaves is created by tiny particles of iron oxides and other pollutants that drift through the air, emanating primarily from eroding vehicle brake pads and diesel exhaust. The particles are small enough to pass through our nasal passages and get lodged in our lungs. Housen and his colleagues found 10 times as much magnetism on urban roadside tree leaves as on their rural counterparts that contend with little traffic.
Housen has also altered his own bike route to campus to avoid the more polluted thoroughfares. “One underlying concern is that if you are riding your bike, you are being more physically active; you are breathing deeper and breathing more air in, and so if you are doing that in an area where there is a concentrated elevation of this material it might not be such a good thing,” he added.
Ironically, many cities that offer dedicated bike lanes often lay them out right next to busy bus lanes, unintentionally ensuring that bicyclists breathe in as much diesel exhaust as possible. “I ride along one of these high-traffic bus routes,” Housen says, “and … there was between two and five or six times more magnetic fine particulate matter along the bus route than [on less-busy streets].” Housen would like to expand his research so it could be used by urban planners to better design bike and pedestrian routes so as not to intermingle so much diesel transit and pedestrian/bicycle traffic.
Of course, there are other ways to track urban pollution levels. In the UK, for instance, researchers from the government-funded Engineering and Physical Sciences Research Council have created the Urban Pollution Monitoring Project, which builds and distributes GPS-enabled mobile pollution sensing systems that can be carried by hand or placed on a bike rack. The group is using data gleaned from the sensors to map where and when pollution levels are at their highest around London and other UK cities, and hopes to use its research to influence the way roads and urban areas are planned in the future as well.
Those who want or need to keep on riding through polluted areas should consider wearing an anti-pollution respiratory mask, many of which can filter out upwards of 95 percent of particulate pollution before it enters the human lung. Some leading manufacturers include Totobobo, G-Flow and Respro.