In southern Arizona, just north of the U.S.-Mexico border, a heat-sensitive remote surveillance camera was recently triggered by a warm body. But it wasn't an illegal immigrant in search of a job, or a courier in the drug trade. It was a jaguar (Panthera onca).
The photograph, taken on August 7, represents the second time in three years that the big cat has been imaged in the U.S. and it raises an intriguing question: Are jaguars seeking U.S. residency?
The southwestern U.S. as far north as the Grand Canyon in Arizona is part of the jaguar's historic range, but since the 1960s sightings of the big cats have occurred at a rate of only about once every ten years.
Wildlife biologists and conservationists believe jaguars largely abandoned the U.S. owing to increased pressure from sprawling development and killing by ranchers seeking to protect their livestock.
"But in last seven years we've had three animals documented here in Arizona, one photographed twice" said Bill Van Pelt, a biologist with the Arizona Game and Fish Department in Phoenix.
In 1996, two hunters independently reported jaguar sightings, which led to development of the Jaguar Conservation Team, a group composed of state wildlife agencies, ranchers, and conservationists interested in the cat's U.S. presence.
"Those two sightings woke a need for some conservation measures, and since then we've been actively looking for them," said Jack Childs, a wildlife researcher in Tucson, Arizona, who sighted one of the jaguars in 1996.
One of the first tasks undertaken by the group was setting up the surveillance cameras, which are triggered when they sense the heat of a body. One of the cameras photographed a jaguar in 2001, providing the first photographic proof that the big cats have a presence in the U.S.
According to a comparison of spots on the jaguar's coat, which serve as a sort of fingerprint, Van Pelt said that the jaguar imaged in August of this year appears to be the same animal imaged in 2001.
"Before no one made a concerted effort at monitoring the border for the presence of jaguars," said Van Pelt. "Perhaps what we are doing is documenting that we have an animal that lives here in Arizona. That is the question we are looking at now."
The closest known population of jaguars to the U.S. lies 135 miles (220 kilometers) south of the border in Mexico's Sierra Madre Mountains. The cats spotted in the U.S. are believed to originate from this population.
"It could be that that habitat is saturated and that the animals are now starting to disperse outside of that population," said Van Pelt.
Most of the jaguars spotted in the U.S. since the 1900s have been males, leading some biologists to believe that males from the Mexican population periodically cross into the U.S. seeking to establish a new territory.
Now that the same cat has been imaged twice, Van Pelt and his colleagues are asking the question of whether or not the male has established a territory in southern Arizona.
Childs, who operates the heat-sensitive cameras, said that the conservation team has increased surveillance of the mountainous area where the jaguar was imaged in August but that no additional sightings have been reported.
The U.S. Fish and Wildlife Service recognizes the jaguar as an endangered species and some conservationists are pushing the government to protect its Arizona habitat, but there are no plans for a jaguar reintroduction effort as was done with gray wolves (Canus lupus) in the 1990s.
A reintroduction effort would require importing wild-caught jaguars from South America to the U.S., but since their habitat and prey base is so different, there is little chance the big cats would survive in the U.S., said Childs.
Alternatively, jaguars from the Mexican population could be brought up to the U.S., but because that population is already endangered, such a move would put the Mexican population in jeopardy.
"But if we can keep our border like it is now, do everything we can, we are hoping they'll colonize on their own as the population increases in Mexico," said Childs. "Maybe those transients will stay up here. Rather than reintroduction, the team is striving for recolonization."
To help achieve this goal, the Jaguar Conservation Team regularly distributes education materials to citizens in Mexico and the U.S. and holds informational seminars in an effort to increase awareness of the jaguars and their potential U.S. home.