Black Bear Conservation on the Mexico/US Border

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In a recent dramatic case, bears from Big Bend National Park, an isolated population in southwestern Texas, made long-range movements to Chihuahua and Coahuila, Mexico, apparently in search of better fall mast. Such movements, especially in fall, are not unusual for black bears, but in this case most of the bears never returned; they either stayed in Mexico, died naturally when crossing the desert, or were poached. As a result, the entire population was reduced to 5–7 bears, including only 2 adult females (Hellgren et al. 2005). Since then, the population has rebounded, possibly by bears immigrating back. Other examples exist where small, seemingly isolated populations have persisted and even grown, from a combination of reproduction and occasional immigration events (Doan-Crider and Hellgren 1996, Onorato et al. 2004).




Northeastern Mexico (Coahuila: Sierra del Carmen range) & southwestern Texas (Big Bend National Park, BIBE)
black bear range.




Ursus americanus, Black Bear, Chisos Basin Window Trail, Big Bend National Park, Brewster County
Texas.

www.flickr.com/photos/tdavenport/5240530690/

Home range and habitat use of American black bears on a desert montane island in Texas

Abstract

American black bears (Ursus americanus) have recolonized Big Bend National Park (BIBE), Texas, in the past 15 years from adjacent habitat in northern Mexico. Range expansion by the Big Bend bear population across the Chihuahuan desert landscape has considerable consequences for the recolonization of areas north of BIBE in western Texas (Glass, Del Norte, and Davis Mountains). We studied black bear ecology from 1998 to 2001 in BIBE. Thirty bears were marked (15 with radiocollars) during the study, including newborn cubs. Home ranges of bears (males mean = 97.7 35.8 km2, females mean = 32.1 4.3 km2) were larger than in southwestern populations in Arizona and northern Mexico, but smaller than those in the nearby Black Gap Wildlife Management Area (BGMWA). Bears were mainly restricted to the Chisos Mountains and their foothills, with 65% of radiolocations in the pinyon (Pinus cembroides)?oak (Quercus spp.)?juniper (Juniperus spp.)?talus?meadow-grass vegetation association. Habitat selection analyses indicated that bears used oak-dominated vegetation types more than expected based upon availability. Bears were more likely than random to be <100 m from anthropogenic features (e.g., roads, trails), but that effect was much stronger in summer when visitor use was low. These data provide predictive capability to managers regarding recolonization of other montane islands north of BIBE and provide information that will help managers ensure the persistence of the small island population of black bears in BIBE.

PDF LINK: www.google.com/url?sa=t&source=web&cd=1&ved=0CCEQFjAA&url=http%3A%2F%2Fwww.bearbiology.com%2Ffileadmin%2Ftpl%2FDownloads%2FURSUS%2FVol_14_2%2FOnorato_Hellgren_14_2.pdf&rct=j&q=Home%20range%20and%20habitat%20use%20of%20American%20black%20bears%20on%20a%20desert%20montane%20island%20in%20Texas&ei=Zed_ToHfNMnx0gHEhuTuDw&usg=AFQjCNG-1HEVXPk8JHyNSoWW6V_buvPong&cad=rja

Black Bear at West Texas Deer Feeder






www.wildlifemanagementpro.com/2008/01/28/black-bear-at-west-texas-deer-feeder/




Population characteristics and winter ecology of black bears in Coahuila, Mexico

Biology, status, and distribution of black bears (Ursus americanus) in Mexico are poorly understood. We studied a population of black bears in the Serranias del Burro, Coahuila, Mexico, from 1991 to 1994 to address the hypothesis that the recolonization source for bears in Texas is the Sierra del Carmen range in northern Mexico. We also described aspects of winter ecology in this southerly population. We captured 42 bears (27 M, 15 F) and equipped 28 with radiotransmitters. All pregnant females (n = 13) and 2 of 5 females with yearlings denned, whereas all other bears, including 10 males, remained active during winter. Mean ( plus or minus SE) den entry and exit dates for pregnant females (n = 5) were 25 December ( plus or minus 5 days) and 22 April ( plus or minus 2 days). Mean age at primiparity was 4.5 plus or minus 0.6 years (n = 4), interbirth interval was 2.0 plus or minus 0.0 years (n = 3), and litter size was 2.75 plus or minus 0.25 cubs/female (n = 12). Estimated adult female and cub annual survival rates were 0.94 plus or minus 0.05 and 0.81 plus or minus 0.10, respectively, based on radiotelemetry and observation of family groups. Estimates of subadult male survival ranged from 0.88 plus or minus 0.08 to 1.00 plus or minus 0.00. We estimated density to be 0.35 bears/km super(2) using a modification of the Lincoln-Petersen estimator that employs animal-equivalents. Because of high reproductive rates and lack of anthropogenic mortality, our data were consistent with the hypothesis that the area can serve as a source of bears emigrating to western Texas. Future bear research in this region should focus on determination of the source of emigrating bears, and identification and conservation of corridors linking Mexican and Texan populations of black bears.

md1.csa.com/partners/viewrecord.php?requester=gs&collection=ENV&recid=3939773&q=&uid=790961554&setcookie=yes





Paw print, Ursus americanus, Sierra del Carmen, Coahuila, México.

www.flickr.com/photos/outfittersmexico/3130222474/



www.nationalgeographicstock.com/ngsimages/explore/explorecomp.jsf?xsys=SE&id=1291623



www.nationalgeographicstock.com/ngsimages/explore/explorecomp.jsf?xsys=SE&id=1291622



Ursus americanus, Sierra del Carmen, Coahuila, México.




Black bear abundance, habitat use, and food habits in the Sierra San Luis, Sonora, Mexico

Description: We studied black bears to determine habitat use, food habits, and abundance between April 2002 and November 2003 in the Sierra San Luis, Sonora. We utilized transects to determine spoor presence, camera traps for abundance, and scat analysis. During 2002, bears fed principally on plant material, and for 2003 on animal matter, namely livestock. Habitat use differed between years and seasons. In general terms, we recorded black bears more frequently during 2002 than 2003, attributing this change to a lack of resources, fruits, and water in our study area.


PDF LINK: www.google.com/url?sa=t&source=web&cd=2&ved=0CCQQFjAB&url=http%3A%2F%2Fwww.fs.fed.us%2Frm%2Fpubs%2Frmrs_p036%2Frmrs_p036_444_448.pdf&rct=j&q=Black%20bear%20abundance%2C%20habitat%20use%2C%20and%20food%20habits%20in%20the.%20Sierra%20San%20Luis&ei=ruN_TpGoFOfi0QHyvfntDw&usg=AFQjCNHghUdfwkMWjIA5wek-IP8pOnA0TA&cad=rja

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From National Park Service - US Department of the Interior


Black Bears Return!

One day in the 1980s, a black bear from the Sierra del Carmen in Northern Mexico started a journey. She descended from the mountains, walked through miles of desert, swam across the Rio Grande, and traversed more desert to reach the forested slopes of the Chisos Mountains in Big Bend National Park. She may have led offspring to the Chisos, and probably encountered a wandering male already using the park's mountain range. How they came and why they came, we may never know. But the return of bears to the park is a remarkable event. It is a success story, and a story of hope for the future.

The Past

In the early 1900s, black bears (Ursus americanus) were common in the Chisos Mountains in Big Bend National Park. Naturalist Vernon Bailey in 1901 described bears as being “... common in the upper canyons of the Chisos Mountains, where fresh tracks of old and young were frequently seen and where there was an abundance of old 'sign' and turned over stones.” Bears continued to be common in the Chisos Mountains through the 1930s.

By the time the park was established in 1944, however, there were virtually no resident bears in the park. Shooting and trapping by ranchers, federal predator control agents, and recreational hunters, and loss of habitat due to settlement and development contributed to their decline. Individual bears occasionally wandered in and out of the park from Mexico, but only scattered sightings were reported from the 1940s through the 1980s. In 1969, and again in 1978, female bears with cubs were seen in the Chisos Mountains. Still, bears were extremely rare in the park.

The Reappearance

The late 1980s brought an amazing turn of events. Visitors began seeing bears in increasing numbers. In 1988, a visitor photographed a female with three young cubs in the Chisos Mountains. On 27 occasions, visitors reported seeing bears that year, more evidence of a resident black bear population. Observations increased in the early 1990s. In 1996, 572 observations were recorded. In 1999 there were 343 sightings of black bears in the park. Once a large animal is eliminated from its natural range, it is rare for it to return on its own. Often, only human intervention can bring back what humans caused to disappear.

The recolonization of black bears in Big Bend is a remarkable natural event. Researchers do not know exactly why the bears returned, but it is due in part to the preservation and restoration of habitat in the park.

www.nps.gov/bibe/naturescience/bears.htm

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National Park Service - US Department of the Interior (Big Bend continued)


Black bears are sighted in many areas of Big Bend National Park, but most live in the Chisos Mountains. The Chisos offer essential components of bear habitat: food, shelter, and water. Black bears thrive in the juniper, piñon pine, madrone, oak, and persimmon trees of the Chisos Mountains and foothills where they find shade and shelter. They eat pine nuts, madrone berries, and acorns, as well as prickly pear fruit, sotol, and yucca. Mountain pools and springs in the foothills provide drinking water much of the year.

Recent studies in the nearby Black Gap Wildlife Management Area has demonstrated that some black bears have also taken up permanent residence in the low elevation desert. Although these are mainly non-breeding bears, at least one female with cubs has used the desert as their normal range.

Through the Seasons

Black bears do not enter a true hibernation in Big Bend. Due to a mild climate and good food availability in Big Bend National Park, black bears are dormant for just three to four months (January-March) each year. Their metabolism slows down during the winter months, and they spend time resting in dens or surface beds. However, they are awake much of the time, and may periodically emerge to find food.

Black bears mate during the summer, so some female bears are pregnant throughout the fall and early winter. The cubs are born in February and stay in the den with their mother until April. The cubs weigh less than one pound at birth, and gain approximately 30 pounds during the first summer. A healthy adult bear in Big Bend can weigh 200-400 pounds and stand five to six feet tall.

There are approximately 8-12 adult bears living in Big Bend, and biologists believe the environment has supported 25 to 30 bears. Though, as with most creatures in a desert environment, there are fluctuations that are bound to occur from time to time.

In order for the bear population to thrive, and to keep humans safe, it is vital that visitors do their part to prevent negative encounters between bears and humans.

www.nps.gov/bibe/naturescience/bearhabitat.htm


Black Bear in Big Bend National Park





Black Bears in the Big Bend Chisos Spring 2011

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Historical and Current Distribution of the Mexican Black Bear (Ursus americanus)




In Mexico, the range of this species spread, some time, further south than at present, covering temperate forests Sierra Madre Oriental, Occidental and adjacent mountains. according to Leopold (1977) in Mexico is distributed in pine-oak forests of the Sierra Madre West coming to southern Zacatecas mountainous desert areas northeastern Sonora, Chihuahua, Coahuila and northern Nuevo Leon, in the forests and underbrush of the Sierra Madre Oriental in southern Nuevo Leon and Tamaulipas. Ramirez et al., (1982) mentions that the three subspecies of bear black is distributed in the states of Chihuahua, Coahuila, Tamaulipas, Sinaloa, Sonora, Durango and San Luis Potosi. Montezuma (1997) cited by SEMARNAP (1999), mentions that populations of this species are distributed in mountainous areas mainly in the valleys and mountains covered with pine and oak as these are the places where food and shelter are available. During the spring and the summer can also be found in the arid range lands that are extend to the foot of the mountains. It is reported that the altitudinal range in which lives, ranging from 650 to 3000 meters.

The historical distribution of the subspecies found in Mexico, U. a. amblyceps was distributed in central and northern states of Sonora and Chihuahua, U. a. machetes in the south and southwest of Chihuahua, Durango, south northwestern Sinaloa and Zacatecas, and U. a. eremicus in the states of Coahuila, Nuevo Leon, Tamaulipas, Zacatecas and San Luis Potosi (Anderson, 1972) (Figure 2).

Once the current distribution of populations of U. americanus in Mexico, little is known. It is reported that the original area distribution has been reduced by 80% and now is found only in northern the country, but there are no precise data about the current distribution actual populations of this species (SEMARNAP, 1999).


Translated from Spanish to English: HAYDEÉ ELIZABETH LOAIZA LÓPEZ (2005).

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Nice write up.......

Bear signs in Big Bend

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Hunger drove Candy from the mountains of northern Mexico, spurred her across huge stretches of uncharitable desert, compelled her to swim the Rio Grande, and pushed her across more rugged ground before she finally reached the promised land of the Chisos Basin in the Big Bend of Texas.

One day in the 1980s, she did what no other female Mexican black bear had done in 50 years. She made the Big Bend her home.

Eventually, fanciful humans named her Candy, although scientifically, she’s known as Bear #7. “She’s the matriarch,” says Dave Onorato, a doctoral student from Oklahoma State University who has spent the last three years studying the bears in Big Bend. It’s his day off and his father’s come to visit, but Onorato’s taking the time to explain his work and show me one of his bear traps. His enthusiasm for the bears emerges in his willingness to venture forth on a freezing morning just to talk about these animals. We take his truck to a trap site, and as he listens for signals from collared bears in the park, he talks about Bear #7. “She came here in about 1984 and started to reproduce in 1988,” he says, which was an important event that helped establish the area as bear habitat. Onorato’s work with the bears indicates that Bear #7 contributed her genes to much of the local population. Although scientists are expected to be dry and detached in their work, he has named his bears: Candy, Little Mama, Trixi, Vixen. Today, we are listening for Hershey’s signal. He is a small yearling male, and at 40 pounds he is about 20 pounds underweight for this time of year.

Before the advent of Bear #7, the conspicuous absence of black bears in west Texas engraved itself as a permanent fact in the minds of residents and visitors alike. Bear #7 and the comeback bears that followed surprised west Texans and the National Park Service. Many of us Texans had learned that in Big Bend, bears had gone the way of the wolf. When a friend of mine, known for his tall tales, claimed to have seen a black bear in Big Bend National Park in 1988, I secretly dismissed his story as an exaggerated javelina sighting. But these days, a yellow sign with a bear silhouette warns of a new presence in the park, unmistakable evidence that the bears are indeed back.

Raymond Skiles, park wildlife biologist, says that as the comeback bears have changed attitudes about living in the Big Bend area, the people in the area have changed their attitudes about the bears. “We’ve seen a different feeling of more welcome from society since the bears came back,” he says, “especially compared to what we find in the records from the turn of the century.” In the early 1900s, black bears disappeared from the area, largely because people killed them or moved into their territories (see sidebar). The bears retreated to Mexico and stayed there for decades before beginning their tentative return to Texas.

It’s a different Texas from the one they left behind decades ago. “There’s a lot of optimism as the bears recolonize west Texas,” says Skiles. “Now we would like to live with them. They enrich our lives, and landowners are willing to consider strategies for managing livestock with bears.” What if bears do become a problem? “Landowners will always have to have some options for dealing with individuals that aren’t compatible,” he says, “but for all parties concerned, we have the attitude that we can get along.”

The bears’ preferred habitat might make that truce a little easier to honor. Their best food sources lie in the park, and the population centers within the park’s boundaries. But how long the bears will stay put in Big Bend is another story.

Onorato tells the story as I follow him to the bear trap on an unseasonably frigid October morning in Big Bend. Later in the day, a winter storm will lock the desert in ice, an unexpected event a week after highs in the area hit 100. “This year, they’ve begun a fall migration,” Onorato says about the bears as we make our way through low-hanging tree limbs and lingering mist. “They’re taking long fall journeys starting around mid-August, and they’re expected to return in mid-November to the natal site. The question is whether or not they’ll come back.” He hopes they will but reports that already four collared bears have died in Mexico where bears are protected in some areas, but not in others. Black bears are protected in Texas.

The fall migration caused the population of bears in the Big Bend area to shift in 2000. Estimates early in the year put the number of bears at about 25, but by November, that estimate dropped to 10 or 15. Females are trekking back to northern Mexico, covering the kind of acreage usually reserved for the more enterprising males. “One female has migrated 100 kilometers (60 miles),” Onorato says, “and that’s very far for a female. Usually, 15 to 20 kilometers is a long way for them to go.”

Why are the bears leaving? Food. Drought and a little caterpillar may have conspired to drive the bears southward. For two consecutive years, the leaf oakworm caterpillar has decimated oaks in key habitat, depriving the bears of acorns, a preferred food. Drought decreased other forage, including the juniper and madrone berries the bears particularly target. As we hike to the bear trap just off the Basin road, Onorato points out the madrones. The deep red bark stands out against green leaves, but it’s true -- no berries are in sight.

“In the fall, it’s important for the bears to put on a lot of weight,” Skiles says. “When acorns are low, they target madrone trees. It’s clear that more wooded, wet areas are very important.” The lingering drought has deprived the bears of this important habitat, possibly sending them south.

Food may have been what drew them north from Mexico in the eighties. “The population stayed strong in Mexico” even after people decimated the bears on the Texas side of the border, says Skiles. “In the forties, the habitat of the area in Texas began to recover from grazing, logging and people living there. It’s hard to say whether the protection of the bears was important or the habitat needed to recover, but after 50 years of seeing mostly migratory males, we started to have more bear sightings.” The population in Mexico may have grown too large for the local food supply, he adds, and large fires in the Sierra del Carmen could have joined the forces that sent the bears northward.

Skiles says that by 1988, the park had 25 sightings in a year, a number that climbed to 572 sightings in 1996. The evening before my hike to the bear trap, a small male appeared just outside the lodge dining hall, pulling visitors away from their dinners as they excitedly watched him through the window.

The small male was breaking the rules, and his appearance so close to civilization in the park was unusual. But, as the park service likes to say, there are no problem bears, just problem people. “We’re extremely pleased with the result of our proactive approach to bear management,” Skiles says. “We’ve had only a few cases where bears have entered a campsite and attempted to get food.” Leaving food around for bears is a people problem that becomes an animal-management issue.

But the park had the advantage of being able to manage an animal population before it was even established. “When the bear population started to grow, we decided we wanted to be the first national park in the country to implement cutting-edge technology before we had a problem,” Skiles says. The park service has a history of doing things wrong when it came to bears -- pictures of grizzlies dining at the garbage dumps in Yellowstone presaged the park’s bear-management difficulties. “The visitors who watched the bears at the garbage dumps didn’t see the aftermath of the ones who got so aggressive that the rangers had to kill them,” Skiles says. “These parks had to go through a painful process to separate people and bears, and they could tell us what we needed to do so we didn’t reinvent the wheel. But no one had ever done this before the problem started.”

Skiles describes a multi-pronged approach to bear management. Education is key. “We want to teach people how to visit the park without having conflict with the bears,” he says. And visitors get an eyeful in every visitor center and in every brochure they see. The park newspaper features a two-page spread on bears, giving advice on how to live safely with wild animals (see sidebar) and providing visitors with updates on bear research. The park even offers a special brochure on the return of the black bear.

In addition to education, Skiles lists staff training, research, and facilities that discourage bear-people contact as paramount in keeping the bears wild. “We train staff to capture and move bears humanely and safely, we’ve changed our waste management from open-top trashcans to bear-proof dumpsters, and we’re using research to develop a scientific basis for our management actions. Our goal is to have a bear population that is wild and is not influenced by human activity.”

But bears can occasionally send even the best-laid management plans awry. “We have had one occasion to relocate a bear,” Skiles relates. “It was an orphan bear that found a great food source -- acorns in a tree near cabins in the park. It was up a tree, drawing a heck of a crowd. People started showing up with picnic baskets, and the fear was that people might feed the bear. So we relocated it to another drainage nearby, hoping it would find another tree. It wasn’t really a problem bear, and the solution seems to have worked.”

Even though the park service’s efforts have been a success, the success of the bear population is not assured. Because Candy/Bear #7 may be the Mother of All Big Bend Bears, the park population could be closely related. Problems with inbreeding and a lack of variation may arise. “Even under the best conditions, this will be a small population,” Skiles says, “although the genetic quality may be OK if migrants from other mountain regions come in.” Skiles also mentions the possibility of bringing in other bears to help improve diversity. “We’ll do whatever is needed in the best interest of the bears here.”

But success is not guaranteed even with all of the careful efforts of the park service. This year alone has seen the loss of one of the park’s most famous bears -- Little Mama -- and her cubs. Newspaper stories about bears in the park had featured Little Mama’s picture, and she was something of a celebrity. “They died in September,” Onorato says, shaking his head. “She died in the desert in a wash, and there were cub prints behind her. We suspect dehydration.”

Little Mama and her kind are members of a keystone species, a species that anchors the ecosystem of an area. If they disappear, the ecosystem gets out of whack. “Black bears eat mostly vegetation, but they are also top predators,” Skiles says, “and they have a big effect on the vegetation community and what is growing where. Their return has made a big step forward.”

The big step forward has not left the bears in the clear. Onorato traps the bears using a combination of irresistible bear attractants, including sardines, tuna and Alaskan Fish Fertilizer, which he sprays around the traps. When he’s trapped a bear, Onorato takes blood samples and analyzes them to establish family connections based on DNA. The results -- which indicate close relationships -- underscore the potential fragility of the Big Bend population.

“We want to get a handle on what the genetic integrity of this population is so we’ll know if the population is diverse enough to sustain itself,” Skiles says. “Our outlook is positive, but guarded.” Skiles estimates that the park can support a population of about 30 bears.

A small population of only 30 bears can make a big difference in the ecological balance of the Big Bend area. “During the period they were missing, there was a big gap,” Skiles says. “When they weren’t here, the park was not complete.”

The bears balance the park for visitors, too. Visits in the eighties delighted with the occasional javelina sighting or frightened with the sound of a unseen rattlesnake, but nothing compares to driving into the Chisos Basin and seeing the now-familiar sign: yellow background with a black bear silhouette. The park wouldn’t be complete without it.


This piece appeared in Texas Parks and Wildlife Magazine.


www.nasw.org/users/ejwillingham/index_files/Page701.htm