Many lizard species will shed their tail as a defensive response
(e.g., to escape a putative predator or aggressive conspecific).
This caudal autotomy incurs a number of costs as a result of
loss of the tail itself, loss of resources (i.e., stored in the tail or
due to the cost of regeneration), and altered behavior. Few
studies have examined the metabolic costs of caudal autotomy.
A previous study demonstrated that geckos can move faster
after tail loss as a result of reduced weight or friction with the
substrate; however, there are no data for the effects of caudal
autotomy on locomotory energetics. We examined the effect
of tail loss on locomotory costs in the Cape dwarf gecko Lygodactylus
capensis (∼0.9 g) using a novel method for collecting
data on small lizards, a method previously used for arthropods.
We measured CO2 production during 5–10 min of exhaustive
exercise (in response to stimulus) and during a 45-min recovery
period. During exercise, we measured speed (for each meter
moved) as well as total distance traveled. Contrary to our expectations,
tailless geckos overall expended less effort in escape
running, moving both slower and for a shorter distance, compared
with when they were intact. Tailless geckos also exhibited
lower excess CO2 production (CO2 production in excess of
normal resting metabolic rate) during exercising. This may be due to reduced metabolically active tissue (tails represent 8.7%
of their initial body mass). An alternative suggestion is that a
change in energy substrate use may take place after tail loss.
This is an intriguing finding that warrants future biochemical
investigation before we can predict the relative costs of tail loss
that lizards might experience under natural conditions.