Predator & Prey

I remember as a kid lining up rows of dominos over and over just to watch them fall in predictable fashion, as each tumbling piece affected the momentum and direction of the next. This domino effect – or chain reaction, I learned later in life – is the cumulative result of one event setting off a succession of other related events. I also learned that similar chain reactions occur in nature, both randomly and by design, and are neither inherently good nor bad – they simply exist.

Predator/prey relationships are a fundamental example, a classic case being the symbiotic relationship between the snowshoe hare and Canada lynx. Lynx numbers rise and fall with cyclic fluctuations in snowshoe hare populations. When hares are abundant, lynx populations expand; when hare numbers crash, lynx must seek alternative food sources, but ultimately their numbers fall.

Nature is full of similar checks and balances designed to establish equilibrium in habitats occupied by various species of plants and animals. Each has a carrying capacity based on the amount and quality of the resources within. Predator/prey relationships, such as the lynx and the hare, and others, provide one balancing mechanism. Prey species by design produce surplus populations and if left unchecked can have a ruinous effect on the habitats they occupy. Predators help keep these animals in balance with the habitat. In turn, the abundance or lack of prey determines the health and well-being of predator populations. As prey populations ebb and flow, they cause chain reactions that can have a far-reaching impact on predatory species and the habitat in which they live.

It shouldn’t come as a surprise that the human component – trappers and fur hunters in this case – also can affect the predator/prey balance by how aggressively they hunt fur-bearing predators, which is often determined by the monetary value of their pelts. In classic domino fashion, shooting coyotes, foxes and bobcats keeps these predator’s populations reduced. But when the fur harvest is reduced – most often due to a decline in fur value – predator populations explode and can have a devastating impact on waterfowl and upland game bird nesting success in the Dakotas, pronghorn fawn recruitment in Arizona and domestic livestock, as examples.

Mike Wilhite, editor and fur market analyst for Trapper’s Post magazine, says fur prices definitely have an impact on furbearer populations. “Many [trappers] won’t trap during low price years so furbearer numbers climb,” he said. “And when predator populations exceed the carrying capacity of the land, game populations suffer and [predators] move on to livestock and domestic pets. Obviously, as a trapper I’m going to hit the trapline harder when fur prices are higher. Being a multi-species trapper helps because I can concentrate efforts on those furbearers that’ll make me some money while letting the others slide for a season.”

But when trappers and fur hunters choose to pull back their efforts, the impact is predictable and often devastating. Some examples follow: A study conducted in North Dakota by Delta Waterfowl examined the effects of predator removal – foxes, skunks and raccoons – had on duck nesting success in areas with marginal grasslands. The project was initiated in the mid-1990s and continued until 2008. According to Joel Brice with Delta Waterfowl, removing the predators from these areas consistently doubled and tripled nesting success compared to blocks of similar land where there was no trapping of these furbearers. Nesting success averaged 70 percent success where predators were trapped, but only 39 percent where no predator control was exercised. In the Nickolaisen Waterfowl Production Area near Cando, North Dakota, predator removal resulted in duck nesting success approaching 80 percent – far above the 15 to 20 percent benchmark needed to sustain populations.

In recent years, the Arizona Game and Fish Department has used lethal methods like ground and aerial shooting to remove coyotes from game management units where pronghorn fawn mortality rates have been exceedingly high. According to Regional Supervisor Raul Vega in Tucson, the department’s intent is to give newborn fawns a chance to survive long enough so they can effectively escape predators.

Vega told Arizona Range News that “Research has clearly and repeatedly shown that coyote-caused fawn predation can be a significant limiting factor affecting pronghorn fawn survival and recruitment rates. It is particularly devastating to populations facing other habitat-related challenges, such as the long-term drought.”

When compared to the five-year average, the fawn-to-doe ratio in the areas where coyotes were aggressively hunted nearly doubled after the removal efforts were initiated just last year, and was the highest it has been in nearly 10 years.

Perhaps even more telling is the effect that rampant coyote populations have on domestic livestock. In 1978 the U.S. Fish and Wildlife Service estimated an economic loss of $19 million to sheep producers from coyote predation in 17 western states. Eleven years later, in 1989, the U.S. Government Account-

ability Office estimated that coyotes in these states killed sheep and lambs valued at $18 million. The National Agricultural Statistical Service (NASS 1991) reported that sheep and lamb losses to coyotes in the U.S. were valued at $18.3 million in 1990. Former sheep producers reported that one of the principal reasons for leaving the sheep industry included high predation losses.

Okay, here’s where it gets interesting. A study conducted by the American Sheep Industry Association showed a positive correlation between the price paid for a coyote pelt and the number of coyotes harvested that year. In 1982, five years before the fur market crashed in 1987, coyote pelts brought an average price of $34.92, and 421,000 coyotes were shot or trapped. A decade later, however, when the average price paid for coyote pelts had dropped to $13.53, the annual harvest decreased to 158,000. That’s a 63 percent decrease in 10 years. As the value of fur pelts plummeted, so did hunters’ and trappers’ motivation to pursue them.

Sheep and lamb losses in states where annual data was available increased from 6.9 percent of the stock sheep and new-crop lambs inventory in 1983, to 11.7 percent of the same inventory in 1994, a 70 percent increase. Again, this is pre- and post-market crash data. Same thing with domestic goats. In three studies in Texas prior to the fur market crash (1985), where an estimated 1.1 million goats (about 90 percent of the goats in the U.S.) are raised, predators were reported to take 18.1 percent of the adults and 33.9 percent of the kids. NASS reported that goat losses to coyotes were valued at $5.7 million in 1990.

Cattle? Yep. According to data released in 2011 by the National Agricultural Statistics Service (NASS), cattle and calf losses from animal predators totaled nearly 220,000 head during 2010. This represented 5.5 percent of the total deaths from all causes and resulted in a loss of $98.5 million to farmers and ranchers. Coyotes and dogs caused the majority of cattle and calf predation, accounting for 53.1 percent and 9.9 percent, respectively.

So data supports the premise that trappers and fur hunters can cause a chain reaction by choosing not to hunt – precipitated by a decline in fur value. Wilhite says that, at least for now, the value of fur is keeping trappers and fur hunters in the field. “The fur market is mainly driven by the trim trade as of late,” he said. “Good western coyotes and bobcats are where the money is. It seems that worldwide demand for good coyotes suitable for parka trim has not been satisfied for the past three or four years.”

Wilhite also points out that the fur markets are fickle and like most commodities fluctuate with supply and demand. “Russia is/was a huge consumer of wild fur, but when the price of crude oil dropped and the ruble depreciated against the U.S. dollar, so did their desire to buy fur,” he said. “Greece, China, and to a certain extent Italy, were making and exporting finished products to Russia so there’s been a trickle-down effect in those countries as well. The value of the U.S. dollar vs. foreign currencies, politics, fashion trends and the weather all play a part in the fur market.” This all determines just how aggressively trappers and fur hunters pursue furbearers.

When predator populations are left unchecked, they can have a devastating effect on game and nongame prey species and domestic livestock. Diseases such as mage, parvo, distemper and others become rampant as coyotes, foxes, raccoons and other fur-bearing predators exceed the carrying capacity of their habitats – nature’s solution for overpopulation. Only when coyotes and other predators are aggressively trapped and hunted – and in some cases, when animal damage control measures are taken – is the balancing act between predators, prey and habitat.

When fur prices are high, hunters enjoy a higher return on their harvest. When fur prices are low and trappers find income elsewhere, predator numbers increase and hunting opportunities soar. So maybe it’s time for fur hunters to help initiate a domino effect that will reduce predator numbers and create balanced, vibrant predator/prey communities by getting out and hunting more aggressively.