Bighorn sheep face challenges like never before
The world of the desert bighorn sheep has changed much in the last 200 years. As well adapted as they are for sheer cliffs and extremes of weather, sheep have struggled with new obstacles brought by the impact of advancing civilization.
Some challenges bighorns face are competition and disease from non-native species, increased fire activity and increased predation.
Burros, cattle, horses, domestic sheep and goats are all species brought to this continent by European settlers. Burros, or wild donkeys, were historically used by miners as pack animals, then they escaped or were set free.
Today, the burro is a famous fixture in the town of Oatman and is frequently encountered in the surrounding area of the Black Mountains. There are also a few wild horses in the area, primarily along the eastern slope of Mt. Wilson.
Burros have done well in the American desert. They have few natural predators, and in the 1970s, the Black Mountains held a large herd, which had a noticeable impact on the habitat of the area.
The Wild Free-Roaming Horses and Burros Act of 1971 gave the Bureau of Land Management responsibility for managing wild burros and horses on its lands in more sustainable numbers.
In 1981, the Black Mountain Feral Burro Herd Management Area was created, with an Appropriate Management Level set at 478 adult burros. Every year, the burro population is reduced to AML levels by roundups that capture animals for adoption through the Adopt-a-Burro program. The BLM conducts surveys every three years using a helicopter and other methods, and they are often assisted by Arizona Game and Fish Department personnel. According to the Kingman BLM, the herd is currently estimated at 478 burros.
While their impact is less today than it was in the past, wild burros can still affect bighorn sheep, especially in times of drought or when sheep are weakened by other factors.
During summer months, both bighorns and burros concentrate near water, increasing both competition for forage and potential displacement of bighorns. Burros can "hole up" near a water source, trampling vegetation and fouling water.
Some domestic livestock can spread disease to bighorn sheep, which may have no immunity to the disease. For this reason, domestic goats and sheep are prohibited in Black Mountain bighorn habitat, but accidents can occur. Decline of bighorn sheep populations due to disease transmission from domestic sheep or goats has been well documented throughout the west. In 1999 and 2001, Game & Fish observed a domestic goat mingling with bighorns in the Black Mountains in hunt unit 15C South and unsuccessful attempts were made to remove the animal.
Population monitoring then revealed a 78 percent reduction of bighorns observed per hour in that unit. Following the 2002 population decline, blood samples were taken from bighorns to monitor disease. Exposure to diseases such as blue-tongue disease (transmitted by biting midges) and epizootic hemorrhagic disease were found to be common.
Game & Fish plans to continue monitoring diseases and to work with BLM to remove any domestic sheep or goats found in bighorn habitat.
Cattle may also impact desert bighorns, though that depends on who you talk to.
The Black Mountains include over a dozen cattle-only grazing allotments, nine of which are yearlong operations.
According to BLM officials, ranchers work with BLM, develop drought strategies and take their cattle off the land temporarily if conditions are dry enough. Bighorn sheep generally occupy more rugged areas and higher elevations than cattle, but in dry places, competition and overlap may exist.
Game & Fish has expressed concern about yearlong livestock grazing in ephemeral habitats in particular. Ephemeral habitats are classified as land below 3,200 feet in elevation and receiving less than ten inches of rain a year.
According to Game & Fish's 2006 Black Mountains Bighorn Sheep Management Plan, nearly 78 percent of the Black Mountains fit that designation. Most of the drier areas are closed to cattle grazing, but there have been some areas of contention, particularly in the area on the east side of the Black Mountains known as Big Ranch A.
In March 2007, the Arizona Game and Fish Commission, which heads Game & Fish, sent out a media release stating that BLM had begun allowing too much cattle grazing in Black Mountain bighorn habitat (especially in Big Ranch A), was not using current data (including recent drought and fires) on the area for management decisions and was not cooperating with them. The Game & Fish letter noted that sheep survey numbers were at 30 percent of normal since the time cattle grazing was reinitiated.
Kingman BLM states that they have been collecting recent monitoring data throughout the Black Mountains, including an evaluation of Big Ranch A in 2003 and a 2006 update of their Black Mountain Ecosystem Plan, and managing things accordingly.
Elno Roundy is project manager of the Mardian Ranch, which owns land and cattle in and near the Black Mountains, including Big Ranch A, and worked for years for BLM in range management. He states that cattle in the area aren't necessarily negative to sheep and points out that livestock waters in the area benefit sheep. He believes that the wildfire that burned big sections of Big Ranch A in 1993 and 2005 is what really hurt the sheep in the area.
In June, several head officials from Game & Fish, Kingman BLM, Mohave Livestock Association, Range Resource Team and others got together in Kingman to discuss bighorn, burro and cattle management. Since that time, according to officials from both the Kingman branch of the Game & Fish and BLM, there has been much more cooperation and coordination of efforts, and the previously noted media release has been rescinded. Don McClure, assistant field manager at the Kingman BLM office, said the groups are now working together towards their common goal of land health. "If we keep the land health, there's enough for all the users (burros, bighorns and livestock)."
Another issue that concerns officials and anyone else who cares about desert wildlife is the issue of wildfire. Fire is often a necessary force in nature, cleaning out old debris and making room for new growth.
However, fire in its current form is not a natural part of the Arizona desert. There was not enough vegetation historically to carry a large fire across wide stretches of desert. That has changed with the invasion of non-native weeds.
Red brome, for instance, is an invasive plant that is fast growing and flammable. It has spread throughout the Black Mountains, and when it dries out in the summer, it creates a vast desert tinderbox just waiting for a spark.
Droughts do not help the situation. When fires strike, they burn hot and fast over large stretches of desert terrain and destroy plants that are not well adapted to deal with them. These fires can damage forage and shelter for animals and blacken areas that may take a long time to recover. Game & Fish reports that 37 wildfires have burned more than 51,000 acres of quality bighorn habitat since 1980.
It is very difficult to deal with invasive weeds. Becky Peck, wildlife biologist at the Kingman BLM, said that several universities are looking into weed control, but no real cure for the problem is known at this time. The Game & Fish Bighorn Management Plan calls for conducting weed surveys and encouraging people to use only established roads and trails when in non-infested areas (weed seeds can be spread by sticking to tires or shoes), using only "weed free" feed for pack animals and cleaning heavy equipment used in weed-infested areas before use in non-infested areas. They are also looking to work with BLM on native plant re-seeding projects in burned areas.
Lastly, there is the issue of predation. While coyotes, bobcats and golden eagles are known to occasionally prey on bighorns, the mountain lion takes the "lion's share" - and gets the lion's share of attention as well. These secretive cats can trigger strong emotions in people, from anger at the loss of big game an individual feels should be going to them instead of to the lion, to awe at the wild beauty of the animal.
Game & Fish is conducting mortality studies of bighorns in the Black Mountains and has recently found a higher-than-usual predation rate by lions. According to Erin Riddering, game specialist for Game & Fish Region 3, lions were responsible for 62 percent of the mortality of radio-collared sheep.
She said that historically, lions may have been more transient in the area, but now there seem to be resident lions year-round. The presence of burros may create an increased prey base to allow this.
Sheep also historically had more mobility than they do now. Riddering said that if individual lions that focus mostly on sheep are killed, a major pressure on sheep will be removed. Game & Fish has implemented hunting seasons with increased bag limits for mountain lions in the Black Mountains to encourage hunters to take more of them, though this has shown a small measure of effectiveness.
According to Game & Fish, other actions are needed as well, including implementing predator control targeted to specific lions. Predator control is a controversial subject, but it can be effective when planned out and targeted to specific areas and individuals. Game & Fish states that predator control would stop once the population has recovered, which is determined by aerial surveys that spot 19.2 sheep per hour (the long-term average from 1981-2000) for two consecutive years. They also plan to put in a proposal to radio-collar and study lion movement in the Black Mountains.
Some of these factors are more easily dealt with than others, but cooperation must occur and action must be taken to help bighorns recover to historic levels and regain the robust numbers they once had.