Ectothermic animals depend on ambient temperature to regulate internal temperature. This dependence affects their ecology and behavior, including locomotion, foraging, and reproduction. Additionally, ectotherms are more vulnerable in environments with extreme hourly temperature fluctuations, and their activity patterns likely match those of favorable temperatures. Here, we studied Pardosa wolf spiders (Lycosidae) in the highland tropical paramos of Costa Rica. We tested two hypotheses to elucidate the drivers of variation in locomotor behavior. First, we tested if locomotor behavior is driven by temperature variation. Spiders experimentally exposed to higher temperatures (30°C) moved 3.96 times faster than those exposed to lower temperatures (7°C). Second, we tested if locomotor behavior is modulated by the maternal care strategy of these spiders. Females carry an egg sac externally by holding it with the distal spinnerets. The egg sac can represent up to 36% of the spider's body size. Females moved at the same speed regardless of whether they carried an egg sac or not. This demonstrates that the maternal care strategy does not affect their locomotor performance. In contrast, temperature plays a crucial role in driving locomotion. These findings expand our understanding of how temperature fluctuations in extreme environments challenge ectotherms’ ability to escape predators and locate potential mates and food.

We ran locomotor behavior trials in which we tested the relative velocity of female wolf spiders of Pardosa sp. (Araneae: Lycosidae). Spiders were experimentally subjected to cold or heat conditions, and we measured their velocity afterward. A portion of those females was carrying an external egg sac that represented up to ~1/3 of their body size. This allowed us to test the effect of carrying that object on their speed.

We conducted this fieldwork in the highland paramo environment of Costa Rica.