"If we ever want this small population to recover, we are going to have to give them their opportunity to cross back and forth," Childs said.
While security is paramount and the impact on the total population limited, Childs said that's not an excuse to knowingly harm an endangered species, The government should implement either political or less damaging solutions to slow illegal immigration.
"It seems senseless to me to have to sacrifice even a remnant population of jaguars," Childs said.
Stoddard dismisses the concerns of environmentalists as a red herring designed to keep the border open.
"Any jaguar, butterfly, deer or other life form that cannot make it over a 12-foot fence needs to be eliminated from the gene pool," said Stoddard.
Efficacy of fences
Both proponents and opponents of border fencing cite a 14-mile fence built near San Diego in the mid-1990s as evidence of the effectiveness - or impotence - of the barriers, There, fencing was followed by a 92-percent decrease in apprehensions from 1994 to 1998.
"If it's well designed, the data shows it works," said Glenn Spencer, president of the Cochise County-based American Border Patrol, a nongov-ernmental organization that keeps tabs on the Border Patrol.
Opponents counter that smugglers simply shifted their routes into Arizona after the fence went up, continuing to sneak drugs and people into the United States at the same rates.
"This is not going to prevent human migration," Miller said, "What it's going to do is funnel and increase human migration into the most rugged and remote regions."
Fences aren't a panacea and don't make sense along the entire border but are a valuable tool in the agency's arsenal, said Brad Benson, a Customs and Border Protection spokesman.
They delay illegal border crossers and give the agency an opportunity to spot and perhaps catch them, he said, Homeland Security envisions a combination of primary fencing, vehicle barriers, technology and agents on patrol as the ideal solution, Benson said.
Public process
The congressional mandate to construct 370 new miles of new primary fencing by November 2008 is driving the urgency to build, Benson said.
Legally, the construction is within the scope of the law, The Real ID Act of 2005 gives DHS the authority to waive environmental regulations that interfere with its ability to fast-track border security projects.
That doesn't ease concerns from those who say the agency is skipping the proper process and using the political mandate as an excuse.
Rep. Raúl Grijalva, D-Ariz., has introduced legislation to counter that trend.
For fence proponents, Grijalva said, "It's one fence fits all regardless of whether you are affecting wildlife, whether you are affecting habitat, whether you are affecting tribal land, There is a process involved: You must consult with public land managers, local communities, with tribes."