Largest faecal impaction (relative to body mass)

A female northern curly-tailed lizard (Leiocephalus carinatus) collected in Cocoa Beach, Brevard County, Florida, USA, on 21 July 2018 was found to contain a faecal impaction, or bolus, in the gastrointestinal tract weighing 22 grams (0.77 ounces). This solid build-up of semi-digested food comprised around 78.5% of the reptile's total body weight (of 28 grams; 0.99 ounces), and is thought to be the largest poo-to-body mass ratio ever documented in a living animal. The findings were reported in the "Natural History Notes" section of the Herpetological Review in March 2020.

After being scanned by a CT machine to establish what was going on inside, the lizard was humanely euthanized as it was clearly suffering and unable to eat. This then enabled an autopsy to be performed. The examination was conducted by herpetologist/ecologist Dr Natalie Claunch of the University of Florida and Ed Stanley of the Florida Museum of Natural History, who happened to be running a wider physiology study into this species.

The scientists put the cause of the extreme faecal impaction down to an unfortunate combination of diet and location. It appeared the lizard had been drawn to the grease in and around the bins of a pizza restaurant, which it had consumed in combination with a lot of sand. Proving this was not a one-off, they had already discovered a similar case on 24 June 2018 in Martin County: another female, this time weighing 30 g (1 oz) with a 14-g (0.49-oz) bolus, equating to 46.7% of the total body mass.

Prior to this, one of the largest faecal boluses found in an animal was removed from a much larger reptile: a Burmese python (Python bivittatus) contained a 6.5-kg (14-lb 5-oz) impaction equating to 13% of the snake's total body weight, as recorded in the journal BioInvasions Records on 21 September 2016.