23 March, 2017

Habitat selection in two Vaejovis species from Arizona

Some scorpions dig burrows, some hide in cracks and crevices in rock walls, other just hide under stones and other suitable surface objects. The reason for a species' retreat choice may be affected by temperature- or climatic preferences, predator pressure, prey availability and similar.

Becker and Brown published a study in December on the factors affecting retreat sites in two species of Vaejovis C. L. Koch, 1836 (Vaejovidae) (V. cashi Graham 2007 and V. electrum Hughes 2011) in Arizona, USA.

The main conclusion is that both Vaejovis cashi and V. electrum selected larger retreat sites that had more stable thermal profiles. Se abstract for more conclusions from this study.

Sky island scorpions shelter under rocks and other surface debris, but, as with other scorpions, it is unclear whether these species select retreat sites randomly. Furthermore, little is known about the thermal preferences of scorpions, and no research has been done to identify whether reproductive condition might influence retreat site selection. The objectives were to (1) identify physical or thermal characteristics for retreat sites occupied by two sky island scorpions (Vaejovis cashi Graham 2007 and V. electrum Hughes 2011) and those not occupied; (2) determine whether retreat site selection differs between the two study species; and (3) identify whether thermal selection differs between species and between gravid and non-gravid females of the same species. Within each scorpion's habitat, maximum dimensions of rocks along a transect line were measured and compared to occupied rocks to determine whether retreat site selection occurred randomly. Temperature loggers were placed under a subset of occupied and unoccupied rocks for 48 hours to compare the thermal characteristics of these rocks. Thermal gradient trials were conducted before parturition and after dispersal of young in order to identify whether gravidity influences thermal preference. Vaejovis cashi and V. electrum both selected larger retreat sites that had more stable thermal profiles. Neither species appeared to have thermal preferences influenced by reproductive condition. However, while thermal selection did not differ among non-gravid individuals, gravid V. electrum selected warmer temperatures than its gravid congener. Sky island scorpions appear to select large retreat sites to maintain thermal stability, although biotic factors (e.g., competition) could also be involved in this choice. Future studies should focus on identifying the various biotic or abiotic factors that could influence retreat site selection in scorpions, as well as determining whether reproductive condition affects thermal selection in other arachnids.

Becker JE, Brown CA. Reliable Refuge: Two Sky Island Scorpion Species Select Larger, Thermally Stable Retreat Sites. PLoS One. 2016;11(12):e0168105. [Open Access]

Thanks to Matt Simon for informing me about this article!

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