Article Review: Do pit vipers assess their venom? Defensive tactics of Deinagkistrodon acutus shift with changed venom reserve

Article Title: Do pit vipers assess their venom? Defensive tactics of Deinagkistrodon acutus shift with changed venom reserves

Authors: Yige Piao, Ge Yao, Hui Jiang, Song Huang, Feng Huang, Yezhong Tang, Yang Liu, Qin Chen

Link: https://www.sciencedirect.com/science/article/pii/S0041010121001732?casa_token=4V_cpYok1GsAAAAA:fTvJRSIdpo2P6oz7QYPest7B1ShkxsUdTIl0o7GdDVeBeVqltcQMzZPd_b0QXDb5l_DdPvCvxG8#sec2

(Chinese moccasin) 

    The authors of this article observed whether pit vipers assessed their venom and shifted their defense tactics based on their venom availability. They took twenty three juvenile Deinagkistrodon acutus (11 males and 12 females) from a snake institute in China. The snakes were exposed to two different stimuli. The first stimulus was a venom expenditure test. They rolled a white paper towel into a cylinder and poked the snakes head once every second until a bite occurred. This was designed to expend the snakes’ venom reserve and was conducted on both a low venom group and a replenishing venom group. The stimulus was weighed before and after the bite on a balance to estimate the amount of venom injected. The second stimulus was a series of behavior trials and was conducted on the low venom group, replenishing venom group and a normal venom group. They stimulus was a piece of medical silicon skin half and was used to mimic predation events, escalating the level of risk over time. The experiment was executed in three consecutive stages, each lasting 60 s. The stimulus was first moved lateral before the subject’s head, then moved toward the subject’s head and backwards, and lastly the stimulus was used to poke the subject’s head once every second. The experiment was stopped at whatever stage the subject struck the stimulus. They observed three different behavioral patterns: active behaviors (attacks), warning behaviors (hiss/tail vibrations) and negative behaviors (retreat).

       The author’s found that the recorded venom amount between groups varied greatly. The maximum venom amount in a single bite was 380 mg, while the minimum amount was 8 mg. For the behavioral aspect of the experiment, they found that the normal venom group displayed a higher proportion of active strikes than both the replenishing and low venom group. They also found that the low venom group had a higher percentage of fleeing behaviors than the two other groups. Warning behaviors were relatively similar between all three groups. 

    The findings of this study showed that venom availability has an influence on the defense tactics of these pit vipers. This experiment allows us to have a better understanding of how these snakes preserve their fitness. They are able to assess their venom amount and make instinctual decisions on what would be best for them physically when it comes to defending themselves against predatory situations. The results are interesting because not many individuals would think that a snake would have the ability to make a decision on when they strike based off how much venom they possess. It’s often assumed snakes strike at any sign of threat.