Adverse effects of Diptera flies on northern ungulates: Rangifer, Alces, and Bison

Abstract

1. Flies (Diptera) damage ungulates far beyond the injury of their bite wounds: they are vectors of diseases and cause ungulates to lose foraging opportunities due to avoidance behaviour. We can use the behavioural and physiological responses of bison Bison spp. (Artiodactyla: Bovidae), caribou/reindeer Rangifer tarandus (Artiodactyla: Cervidae), and moose/elk Alces alces (Artiodactyla: Cervidae) to assess the impacts of flies on these ungulates. Ungulates rely on morphological and physiological resistance to flies at lowintensities of exposure. However, as fly exposure increases, ungulates begin to react with behavioural avoidance in addition to increasing their physiological response. Rangifer tarandus are highly sensitive to flies and respond quickly to their presence by avoidance behaviours that incur fitness costs through reduced body mass. Alces alces are less reactive to fly exposure, enduring the presence of flies and maintaining a low loss of fitness, sometimes dying from the cumulative effects of exposure. Bison spp. may use a facultative strategy that depends upon the prevalence of flies and associated diseases in their environment. Among these strategies, variables such as the type of fly bite, presence and degree of infection, and heritability of resistance affect individual host survival. 3. Relationships between flies and ungulates can integrate multiple scales of organisation in the ecosystem to reflect system stability. Climate change is predicted to alter the species composition and seasonal phenology of flies and the associated effects of wounding and vector-borne disease on ungulate populations that are central to the functions of Arctic and temperate ecosystems in the Northern Hemisphere.

Sores of boreal moose reveal a previously unknown genetic lineage of parasitic nematode within the genus Onchocerca

“…Morphological barriers such as skin and hair are the first line of defense used by ungulates to resist flies [ 1 ]. Moose calves do not develop sores, likely because their skin is covered by hair throughout the summer [ 26 ].…”

“…A mammal’s coat and integument is an important barrier between the animal and its environment, providing protection against pollutants, extreme temperatures, pathogens, and irritants such as insects [ 1 – 3 ]. Hair and melanin in the integument offer thermoregulation and photoprotection.…”

Trapped between food, heat, and insects: Movement of moose (Alces alces) and exposure to flies in the boreal forest of Alaska

“…The effects of people, wolves, and bears on moose populations are well studied (Boutin, 1992 ), but much less is known about the effects of flies (Diptera) that can alter both behavior and physiology of ungulates (Samuel et al., 2001 ). The skin and coat is the first line of defense against flies; breaks in this barrier, either from injury or molt, leave the animal vulnerable to flies (Benedict & Barboza, 2022 ). Fly contact or bites can result in allergic reactions, blood loss, secondary infection, restricted breathing, pneumonia, peritonitis, and neurological impairments, all of which can decrease body condition to reduce birth rates and increase death rates in a population (Ezenwa, 2004 ; Samuel et al., 2001 ).…”

“…As fly exposure increases, many ungulates react with behavioral avoidance (Benedict & Barboza, 2022 ). In the presence of flies, bison ( Bison bison ) trade‐off foraging for wallowing, grooming, and standing (McMillan et al., 2000 ; Meagher, 1973 ; Melton et al., 1989 ).…”

“…Moose appear less reactive and more tolerant to flies than caribou and bison (Benedict & Barboza, 2022 ). Moose do not make large‐scale movements to evade flies even though an individual moose may be surrounded by thousands of flies at any one time in the summer (Benedict et al., 2024 ; Benedict & Barboza, 2022 ). However, we do not know if moose make small scale movements and habitat choices in response to flies, or a particular type of fly.…”