Are pumas subordinate carnivores, and does it matter?

1. What they did

Pumas share their range across North and South America with other large carnivores, and in many places people also hunt them. Gray wolves and grizzly bears are now spreading back into parts of North America where pumas are already managed through hunting. The authors asked whether pumas are the “boss” in these relationships or the underdog (the subordinate species), because a subordinate species may already be paying a cost that hunting adds to.

They had three aims:

• Review the evidence. They searched the published literature for signs of who dominated whom when pumas met six other apex predators (carnivores over 15 kg): gray wolf, grizzly bear, American black bear, jaguar, coyote and maned wolf. They predicted that larger and social (pack-living) carnivores would dominate pumas.
• Look at smaller cats. They did the same for three felid mesocarnivores with similar ecology: bobcat, Canada lynx and ocelot.
• Map it. Using International Union for Conservation of Nature (IUCN) range maps and a Geographic Information System (GIS), they worked out in what part of the puma’s range pumas live alongside at least one species that dominates them.

Because papers rarely made it possible to tell different kinds of competition apart, the authors grouped the evidence into two kinds: non-lethal competition (for example being chased off a kill, having food stolen, changing where or when they are active, or changing diet) and lethal competition (one species killing the other, whether or not it eats it). For each pair of species, dominance went to the species with the most publications supporting it.

2. What they found

Apex predators (64 sources)

• Gray wolves dominated pumas in 18 of 23 sources (78%). Pumas dominated wolves in 5 (22%), all reports of pumas killing wolves.
• Grizzly bears dominated pumas in all 4 sources.
• Black bears dominated pumas in 6 of 9 sources (67%); pumas dominated black bears in 4 (44%), through pumas killing bears.
• Jaguars dominated pumas in 15 of 25 sources (60%). The other 10 found no sign that either species dominated. Five sources reported jaguars killing pumas; the authors found no report of the reverse.
• Coyotes dominated pumas in only 3 of 16 sources (19%); pumas dominated coyotes in 13 (81%).
• Maned wolves never dominated pumas; pumas dominated them in 2 of 3 sources, and 1 found the two equal.

Smaller cats (13 sources)

Pumas appeared dominant over all three. Three sources reported pumas killing ocelots (two others suggested the two may not affect each other), one reported a puma killing a Canada lynx, six reported pumas preying on bobcats, and three reported pumas pushing bobcats out of areas.

What subordination looked like for pumas

• Being displaced from their kills, or having kills taken (kleptoparasitism), by wolves, bears and sometimes packs of coyotes.
• Shifting where they lived and hunted, and switching prey, where wolves were present.
• Starvation linked to competition with wolves, and wolves killing pumas of all ages.
• Bears and coyotes occasionally killing puma kittens. In the authors’ own unpublished data, a black bear killed and ate three kittens of one litter.

Body size

Size could not be tested directly, because pumas and other carnivores differ greatly between males and females, sources often did not report sex, and pack size was often missing. The general pattern still suggested size matters: jaguars dominated most clearly where they are much larger than pumas, and wolf packs had a clear advantage, while one wolf against one puma was less certain.

The map

Pumas are subordinate to at least one other apex carnivore in 10,799,252 km², or 47.5%, of their 22,735,268 km² range.

3. What they concluded

• Pumas are subordinate to some apex carnivores (gray wolves, grizzly bears, black bears and jaguars) and dominant over others (coyotes and maned wolves), as well as over bobcats, Canada lynx and ocelots.
• Wolves appear to affect pumas most, probably because they live in packs and often outnumber them. Wolf harassment may cost a puma about five times the energy of normal hunting (from another study). Bears seem to have less effect, partly because they are dormant for part of the year, giving pumas a seasonal break.
• Many jaguar and puma studies used camera traps and scat analysis rather than marked animals, which likely explains why so many found no competition.
• Humans also dominate pumas: hunting affects their populations and dispersal, and people are generally the leading cause of puma deaths even where pumas are not hunted.
• Despite the evidence of costs, no research yet clearly links competition to puma fitness (survival and breeding), or looks at competition and human hunting together. The review mostly shows how little is known.

6. Other technologies, skills or innovations

• A structured literature review that sorts evidence of competition into non-lethal and lethal outcomes for each species pair.
• Geographic Information System (GIS) analysis in ArcGIS 10.0, combining IUCN range maps to map where pumas live alongside dominant competitors.
• Drawings of the apex predators in Figure 1 are by Mark Elbroch.

7. Implications for conservation (from the paper)

• If pumas are subordinate to wolves or bears that are recovering in an area, managers may need to adjust hunting limits to allow for the extra pressure of new competition.
• Until it is known whether competition and human hunting add together, or even make each other worse, the authors encourage caution in setting hunting limits for pumas and other subordinate apex carnivores where they share range with dominant species.
• This matters most where wolves and brown bears are coming back and older competition between several large carnivores is returning.
• They call for more research on competition among apex predators, especially where pumas and other predators are also hunted.