Sauropod Vertebra Picture of the Week

I got an email a couple of days ago from Maija Karala, asking me a question I’d not come across before (among several other questions): how much poop did Argentinosaurus produce in a day?

I don’t recall this question having been addressed in the literature, though if anyone knows different please shout. Having thought about it a little, I sent the following really really vague and hand-wavy response.

Suppose Argentinosaurus massed 73 tonnes (Mazzetta et al. 2004). In cattle, food intake varies roughly with body mass to the power 0.7 (Taylor et al. 1986), so let’s assume that the same is true of sauropods.

Let’s also assume that sauropods are like scaled-up elephants, in that both would have subsisted on low-quality forage. Wikipedia says elephants “can consume as much as 150 kg (330 lb) of food and 40 L (11 US gal) of water in a day.” Let’s assume that the “as much as” suggests we’re talking about a big elephant here, maybe 6 tonnes. So Argentinosaurus is 73/6 = 12 times as heavy, which means its food intake would be 12 ^ 0.7 = 5.7 times as much. That’s 850 kg per day.

Hummel et al. (2008, table 1) show that for a range of foods, the indigestible “neutral detergent fibre” makes up something around half of the mass, so let’s assume that’s the bulk of what gets pooped out, and halve the input to get about 400 kg of poop per day.

References

• Hummel, Jürgen, Carole T. Gee, Karl-Heinz Südekum, P. Martin Sander, Gunther Nogge and Marcus Clauss. 2008. In vitro digestibility of fern and gymnosperm foliage: implications for sauropod feeding ecology and diet selection. Proceedings of the Royal Society B, 275:1015-1021. doi:10.1098/rspb.2007.1728
• Mazzetta, Gerardo V., Per Christiansen and Richard A. Farina. 2004. Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs. Historical Biology 2004:1-13.
• Taylor, C. S., A. J. Moore and R. B. Thiessen. 1986. Voluntary food intake in relation to body weight among British breeds of cattle. Animal Science 42(1):11-18.

You could drive several trucks through the holes in that reasoning, but it’s a start. Can anyone help to refine the reasoning, improve the references, and get a better estimate?