Hoary Marmots Attracted to Human Urine Sites

Abstract

Accounts of foraging behavior in hoary marmots (Marmota caligata) show very similar patterns in colonies from Alaska (Hansen 1975; Holmes 1984a), Montana (Tyser and Moermond 1983), and Washington (Barash 1973,1974; Taulman 1975). All members of a colony have equal access to foraging areas as a result of the high social tolerance between colony members (Barash 1974). Selection of primary feeding areas is influenced by the abundance of preferred plant species and by the proximity of refuge and sleeping burrows (Holmes 1984a). Marmots typically move about while feeding, looking up about once a minute to reconnoiter their surroundings as they chewJ before moving on a few steps (Taulman 1975; Tyser and Moermond 1983; Holmes 1984a). This paper presents new data on hoary marmot feeding behavior at human urine sites. From 18 June through 20 September 1975 I spent 322 hrs observing the behavior of a colony of four adult and three yearling hoary marmots on the south slope of Mt. Cashmere in the Washington Cascades at an elevation of 2200 m (47°32'N, 120°50tW). I observed 19 instances of from one to four marmots at a time feeding at human urine sites. The sites were often bare ground, and the marmots appeared to be nibbling or licking the soil, occasionally scratching at the dirt. While feeding at a latrine site, marmots assumed a characteristic posture seen at no other time. They crouched with the forepaws together under the body in a cat-like stance. A feeding marmot appeared motionless for 5-10 min at a time, not looking up or moving around, as is normally seen in foraging or traveling behavior. Pattie (1967) reported on a group of yellow-bellied marmots (Marmota faviventris) feeding regularly along a roadside where they may have been picking up traces of salt. He substantiated this theory with further observations that yellow-bellied marmots, as well as pikas (Ochotona princeps), golden-mantled ground squirrels (Citellus saturatus) and mule deer (Odocoileus hemionus) visited latrines and ate both dirt and vegetation where humans had urinated. Another researcher (Holmes 1984b) found that hoary marmots would enter traps baited with human urine after the spring thaw, when 14 other previously-taken baits were no longer effective. To test the hypothesis that the approximately 0.7% salt normally found in human urine was the attractive ingredient, I mixed enough salt in 0.5 l of water to produce a slight salty taste and poured this on a plot of bare ground within 30 m of the sleeping burrows. A similar site 1 m from the experimental plot received an equal amount of unsalted water. The next day two marmots, and again seven days later one marmot, fed at the site that had received the salted water. Each marmot showed the same novel feeding behavior as did marmots at urine sites. No marmots were observed to notice the control plot. Hoary marmots presumably obtain salt in trace amounts from rocks and soil, but they are attracted to the higher concentrations available in the soil at human latrines. Normal foraging behavior is not appropriate because of the small size of the urine sites; thus, animals remain stationary when feeding. Urine sites utilized were near the marmots' sleeping burrows since that part of the colony territory provided an excellent vantage point for observations. ThereforeJ marmots feeding at urine sites had a familiar refuge nearby. The fact that the customary head-up alert posture seen during normal foraging was not performed by marmots feeding at urine plots implies the possibility that