Body condition and head size in snakes
On several occasions during my many years of working with various snake species, I observed a significant positive relationship between body condition and head size (the former calculated from residual scores from a general linear regression of In-transformed mass on In-transformed snout-vent length). Based on results from my long-term study of water pythons (basis fuscus) this relationship is, however, most likely caused by a condition-dependent bias when recording snake snout-vent length (SVL). Water pythons in good condition were recorded as being "shorter" and hence having relatively larger head size, whereas snakes in poor condition were recorded as being "longer" with concomitant smaller head relative head size. Such a systematic bias may lead to spurious conclusions concerning the adaptive significance of the relationship between snake body condition and head size.