Abstract
Interspecific competition may occur when resources are limited, and is often most intense between animals in the same ecological guild. Intraguild predation (IGP) is a distinctive form of interference competition, where a dominant predator selectively kills subordinate rivals to gain increased access to resources. However, before IGP can be identified, organisms must be confirmed as members of the same guild and occur together in space and time. The lesser hairy-footed dunnart (Sminthopsis youngsoni, Dasyuridae) is a generalist marsupial insectivore in arid Australia, but consumes wolf spiders (Lycosa spp., Lycosidae) disproportionately often relative to their availability. Here, we test the hypothesis that this disproportionate predation is a product of frequent encounter rates between the interactants due to high overlap in their diets and use of space and time. Diet and prey availability were determined using direct observations and invertebrate pitfall trapping, microhabitat use by tracking individuals of both species-groups, and temporal activity using spotlighting and camera traps. Major overlap (greater than 75% similarity) was found in diet and temporal activity, and weaker overlap in microhabitat use. Taken together, these findings suggest reasonable potential, for the first time, for competition and intraguild predation to occur between taxa as disparate as marsupials and spiders.
Highlights
Interspecific competition may occur when resources are limited, and is often most intense between animals in the same ecological guild
Major overlap was found in diet and temporal activity, and weaker overlap in microhabitat use. These findings suggest reasonable potential, for the first time, for competition and intraguild predation to occur between taxa as disparate as marsupials and spiders
A total of 10 S. youngsoni was followed during October 2016, May and October 2017, with prey capture witnessed on 13 occasions
Summary
Interspecific competition may occur when resources are limited, and is often most intense between animals in the same ecological guild. Major overlap (greater than 75% similarity) was found in diet and temporal activity, and weaker overlap in microhabitat use Taken together, these findings suggest reasonable potential, for the first time, for competition and intraguild predation to occur between taxa as disparate as marsupials and spiders. In Australian systems the larger and dominant dingo (Canis dingo) will kill and sometimes consume the invasive red fox (Vulpes vulpes), thereby reducing competition for shared prey [18,19] These interactions are usually asymmetric and facilitated by differences in body size, with killing often arising when the larger carnivore is 2–4 times the size of the subordinate [14,17]. IGP may develop as a consequence of encounter rates escalating with increased overlap in niche use [24,25]
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