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Tigers take to the night in order to thrive among humans

A new study suggests that endangered carnivores and humans can share habitats.

As the human population grows, conflicts with wildlife are becoming more common and more intense. Many conservation models are built on the idea that threatened species, especially large carnivores, cannot successfully use the same habitat as humans. These theories claim that large protected areas are needed to ensure the survival of these species, so parks have been fenced and humans have been resettled.

However, in a new study in PNAS this week, scientists from Michigan State University raise the possibility that this conservation model may not be the only one that works. Since 2010, these researchers have been tracking the behaviors of both tigers and humans in and around Chitwan National Park in Nepal. Their findings suggest that humans and tigers can coexist at very fine geographical scales, thanks to small changes in the tigers’ behavior.

To determine the behavioral patterns of each species, the researchers employed almost 80 camera traps both inside and outside the protected area. These motion-sensitive cameras documented each time a human or a tiger was in the immediate vicinity; this allowed the researchers to examine coexistence at a very fine spatial scale. In this area, human activities include tourism, research, military activity, and the collection of firewood by locals.

The researchers found that tigers and humans were frequently caught by the same cameras, indicating that both species were using the same paths and roads. Surprisingly, tiger density was not any higher inside the park, where human activity is limited, than it was outside the park, where human use is much more frequent. Furthermore, tiger density and human use of the area appear to be much higher in the Chitwan area than they are in other parts of the tigers’ range. Here, the two species appear to be able to coexist, and in fact thrive, in each others’ presence.

A second finding suggests a potential reason for this successful coexistence: the tigers in this study were most active early in the morning and late at night, when human activity was at its lowest. This pattern of behavior is not the norm for this species; the tigers in Chitwan were about 17 percent less active during the day than tigers in other, less-populated areas. This suggests that where human use is high, tigers may be able to adjust their behavior in order to avoid humans. Tiger density remained high over the course of the study (and in fact increased during the second year), suggesting that the changes do not appear to negatively impact the tigers’ success, at least over a short time scale.

However, the study’s authors warn that much more research is needed before larger generalizations can be made. Obviously, the long-term effects of the tigers’ behavioral changes are unknown. Additionally, although Chitwan National Park was an ideal study site in many ways, it differs greatly from tiger habitats in other parts of the world. In the last two decades, Chitwan National Park has employed new forest management policies which have increased both forest biomass and prey density, two factors that are likely to enhance tigers’ ability to thrive in and around the park. Additionally, tiger poaching has been tightly controlled in Nepal since 2006. Human-tiger dynamics may differ in areas without similar levels of park management, local economic activities, and carnivore tolerance that are seen in Chitwan.

Although somewhat limited in scope, this study suggests that the all-or-nothing conservation plans that separate human habitat from that of threatened species may not be the only way to proceed. It offers some hope that as we move into the future, humans and large carnivores may be able to share the same landscape.

Article abstract:

Many wildlife species face imminent extinction because of human impacts, and therefore, a prevailing belief is that some wildlife species, particularly large carnivores and ungulates, cannot coexist with people at fine spatial scales (i.e., cannot regularly use the exact same point locations). This belief provides rationale for various conservation programs, such as resettling human communities outside protected areas. However, quantitative information on the capacity and mechanisms for wildlife to coexist with humans at fine spatial scales is scarce. Such information is vital, because the world is becoming increasingly crowded. Here, we provide empirical information about the capacity and mechanisms for tigers (a globally endangered species) to coexist with humans at fine spatial scales inside and outside Nepal’s Chitwan National Park, a flagship protected area for imperiled wildlife. Information obtained from field cameras in 2010 and 2011 indicated that human presence (i.e., people on foot and vehicles) was ubiquitous and abundant throughout the study site; however, tiger density was also high. Surprisingly, even at a fine spatial scale (i.e., camera locations), tigers spatially overlapped with people on foot and vehicles in both years. However, in both years, tigers offset their temporal activity patterns to be much less active during the day when human activity peaked. In addition to temporal displacement, tiger–human coexistence was likely enhanced by abundant tiger prey and low levels of tiger poaching. Incorporating fine-scale spatial and temporal activity patterns into conservation plans can help address a major global challenge—meeting human needs while sustaining wildlife.

Full article pdf available at:


by - Sept 4 2012