Large Mammals in the North: Climate Change and Bottom Up and Top Down Influences

Abstract

the literature indicates a continued controversy whether ungulate populations are controlled from the bottom-up or the top-down and whether wolf predation is benefi cial removing sick and unfi t in-p or the top-down and whether wolf predation is beneficial removing sick and unfit individuals or detrimental, driving populations into the so-called "predator pit". a macro-ecological approach was used to address these questions supporting the following conclusions: ungulates have evolved at the biome spatial scale, late and early succession specialists occur in each biome, one is larger and one is smaller, historically wolves occurred in all North american biomes as primary predators of ungulates, wolves specialize on the most common ungulate species, wolves change morphologically in relation to the size of their primary prey, pack size changes in relation to the size of their primary prey, wolf predation can be beneficial or detrimental depending upon the numerical and size relationship between the ungulate species in the system. Climate changes such as fire, drought and insect infestation will create early successional habitat increasing early successional specialists numbers and decreasing late successional ungulate population numbers. Bottom-up and top-down forces exist in all populations where wolves occur and managers need policies that support the smaller sized ungulate in the ecosystem, if they want to maintain both species at stable or increasing population levels.

Morphological relationships among populations support a single taxonomic unit for the North American Gray Wolf

“…Prey size has been reported to influence gray wolf size (Schmitz and Kolenosky 1985; Kyle et al 2006; Wiwchar and Mallory 2012; Mallory et al 2019). In this study, large-sized skulls are more frequent where large ungulates (bison, moose, and elk) abound, in boreal and montane forests; medium-sized and small-sized skulls prevail in habitats with higher frequencies of smaller ungulates, in AT (caribou and muskox), and Tf (mule deer, black-tailed deer, and white-tailed deer; Naughton 2012).…”

“…The gray Wolf ( Canis lupus ) diverged from Canis etruscus about 800,000 years ago in Asia, then extended its range to different parts of Asia and Africa (Kurtén and Anderson 1980; Paquet and Carbyn 2003; Wang and Tedford 2008). Over time, from at least the Late Pleistocene (Kurtén and Anderson 1980), the species evolved toward hypercarnivory and increased in size to specialize in killing and feeding upon large ungulates and became the largest member of the extant family Canidae (Mech 1974; Van Valkenburgh and Koepfli 1993; Brooke et al 2014; Mallory et al 2019). Such a correlated increase in hypercarnivory and body size acts like an evolutionary ratchet–after a lineage evolves toward specialization on larger prey, a larger body size evolves over time, and size reaches an upper limit with no reverting possible (Stanley 1979; Van Valkenburgh et al 2004; Van Valkenburgh 2007).…”