Construction of a low cost and highly sensitive direct heat calorimeter suitable for estimating metabolic rate in small animals

•We constructed a low cost and highly sensitive direct heat calorimeter for estimation of metabolic rate.•The device employs an inexpensive thermoelectric cooler (Peltier device) and relies on a heat differential to drive an electrical potential (Seebeck effect).•Output potential increased predictably with increasing input power.•The limit of detection is 0.088 J s−1 with 95% confidence.•The calorimeter can reliably estimate heat production in small animals such as rodents.

Although the concept of a metabolic rate is readily understood, actual measurement of metabolism has proved much more difficult. The numerous strategies for estimation of metabolic rate all result in an incomplete accounting. Respirometry or gas exchange is the most widely used approach but mostly ignores the anaerobic component. Here, we describe a readily-built and low cost direct heat calorimeter that may be coupled with standard respirometry equipment to provide a more complete portrait of metabolism. The device is sensitive and provides a predictable measurement of heat flow from an organism.