Palaeontologists seem to know a great deal about what dinosaurs ate or how they moved, but I can't remember ever reading about how dinosaurs did their business, and I can't imagine it was because of modesty's sake either. So...any thoughts?

I don't think there really is a way to scientifically test how dinosaurs copulated. Except perhaps through analogies drawn from their modern relatives. On the other hand biomechanical modeling could predict maximum stresses applied to the skeleton during copulation, thus allowing scientists to say, 'Well dinosaurs couldn't possibly have copulated in this way, because that would excede the maximum stress value, but this other way may have been possible because it's within the safe range.' R. McNeil Alexander has a bit on this in his Dynamics of dinosaurs & other extinct giants (Columbia University Press).

Manabu wrote that "biomechanical modeling could predict maximum stresses applied to the skeleton during copulation, thus allowing scientists to say, 'Well dinosaurs couldn't possibly have copulated in this way, because that would excede the maximum stress value, but this other way may have been possible because it's within the safe range.'"

I just want to point out how very approximate such calculations are, though, before anyone gets too excited.  For example, one paper (Economos 1985) calculated the theoretical maximum mass for a terrestrial animal at 15 tonnes, while a followup (Hokannen 1986) yielded estimates between 100 and 1000 tonnes.  Similarly, the masses of the animals involved have been estimated at wildly warying levels: for example, Brachiosaurus brancai has been estimated everywhere between 15 tonnes (Russell et al. 1985) to 78 tonnes (Colbert 1962).  So we need to be very, very careful when working with these numbers.

Taking this to an extreme, I once calculated the safety factor why which sauropod dinosaurs could walk without crushing the articular cartilage in their limbs ... and when I'd evaluated the sources of possible error, concluded that my results were "correct within a factor of 756" :-)  Admittedly that is stretching a little to make a rhetorical point, but it should at least serve as a warning.

For anyone who's interested, by the way, the slides for the talk with that calculation in are at … rength.ppt
I think they should be pretty comprehensible to an intelligent non-specialist.

Hi Joon,
You have hit on an important area of research though, and one that continues to fascinate people, how do you do things necessary for survival, when you are the size of a dinosaur. 
I have been thinking about this question for a few days now, and did not want to answer at first, because I am not a specialist in Dinosaurs.  However, to answer your question- 'How did dinosaurs copulate?"- literally, there are several possible answers.  The first is 'succesfully', because the dinosaurs as a whole spanned the Triassic, Jurassic and Cretaceous.  So they must have been doing something right. 
Now I enter the realm of speculation, on my part, but I will use Manabu's suggestion of using living analogues.
The smaller Theropods, may have accomplished the task in much the same way as birds today.  The larger Sauropods, and many Ornithischians, may have adopted a more 'elephantine' technique.  Finally the group that puzzles me most is the Stegasaurs.  I cannot think of a modern analogue, so  I guess they just did it 'carefully'. 
The largest animals alive today support their weight by living in water, so the only thing I can think of for comparisson, for dinosaurs, are the large African mammals; Rhinos, elephants and hippos, for comparisson to mid-sized dinosaurs. Birds for the smaller to medium theropods (ostriches may make a good analogue).  As Manabu says, there is no real scientific means of answering your question.  I hope that I have not offered too wild-an answer.

Last edited by Neil Gostling (21st May 2007 17:04:39)

In regards to Neil's humorous statement on how Stegasaurs copulated (carefully:), the best modern analogue I can think of in terms of awkwardness may be a porcupine, they manage to do it despite those big crazy quills!

I've been working closely over the past few years with an ethologist (animal behaviourist) who is doing a master's thesis on sexual behaviour in dinosaurs. No, really! I cannot yet give all the details away, but his method essentially involves reconstructing the soft-tissue anatomy of male and females dinosaurs (this is largely speculative and based on what is present in living crocodilians and birds combined with what makes biomechanical sense), and then working out which postures might work given the diversity of body shapes. In fact there is a long and surprising tradition of palaeo-sex reconstruction.

Note that mammals are, generally speaking, poor analogues for dinosaur sex, and that crocodilians and birds presumably serve better. Unlike elephants and rhinos, it is unlikely that big dinosaurs took a great deal of time when mating (it simply doesn't work this way in crocodilians and birds), and it is also unlikely that males had particularly immense or flexible sex organs (though they were still big enough, than you very much). Because of the large tail, it is most likely that dinosaur females lowered their hindquarters toward the ground (unlike many mammals, where the female raises her rump well off the ground). The male presumably straddled the tail base and aligned his cloaca with that of the female before a brief act of intromission. We can only marvel at how stegosaurs and the bigger sauropods mated - again, there are lots of ideas in the dinosaur literature, but at the moment it is all speculation.

I could go on, but I wouldn't want people to get the wrong idea. I hope this was helpful.

Last edited by Darren Naish (22nd May 2007 21:05:31)

That's cool. When you reconstruct dinosaur sex, we automatically assume an upright posture as in many mammals. It's interesting how mammalian copulation method is the first thing that springs to mind, maybe we see it more often on nature shows than we do of crocs or birds?

Since Luis Rey is too busy to do it for himself, here it a link to an image he created on this very subject with the very cool theropod dinosaur Carnotaurus.

Bob Bakker also did some drawings of possible dinosaur mating positions (with stegosaurs!) for his 'Dinosaur Heresies' book, but sadly I can't find any online.

The great biomechanicist McNeil Alexander is infamous for demonstrating sauropod mating in one of his lectures in Leeds - assisted by his wife according to rumour. Unfortunately I missed that one, but I can well imagine it being very informative (and entertaining).

The difficulty is of course that absolutely everything relating to this subject is pure speculation with no possibility of being proved. At best a hypothesis can be considered plausible given the known limitations. Let's just hope that dinosaurs didn't use a novel method of transferring sperm (for example in a packet that the female could insert into her cloaca, or any other crazy mechanism), because we would never know it if they did.

No no no - not McNeil Alexander: Beverley Halstead (unless I'm horribly mistaken). Halstead published several articles on dinosaur sex and his on-stage performances were legendary.

No - I think we might both be right. I vaguely recall a story that Beverly Halstead got McNeil Alexander to be the mate for the demonstration (or vice versa). McNeil is a tremendous speaker and showman and it's the kind of thing he's done in talks I've seen him present in Leeds.

Well the basic problem is this.  If you don't have an intromittant organ (ie. a penis), or if it's relatively short (eg. lizards, crocodiles) you need to bring your sexual opening (ie. eg. cloacal opening) into very close proximity with one possessed by a member (no pun intended) of the opposite sex.  If you watch birds copulate they have to do some serious twisting to line things up.  Lizards are basically similar - the male twists his pelvis around the female's, who usually either raises her tail or twists her tail sideways, so that their vents almost touch allowing the male to insert a hemipenis.

Crocodilians, being generally very large, can't usually do this on land and therefore copulate in water.  The added buoyancy assists the male in rolling the female over slightly, allowing him to twist his own body at a sufficient angle that his vent comes into close contact with hers, allowing him to insert his relatively short penis.

It's likely that dinosaurs probably used a variety of copulation techniques, and some (especially the larger ones) would have been trickier than others.  Perhaps some of them used water for added buoyancy, or were sufficiently limber to be able to contort their bodies to allow mating, but I'm sure there was a lot of diversity out there.

Or perhaps they developed a large prehensile penis-like structure which solved the problem relatively simply. The problem is that we wouldn't know unless it had hard parts (no pun intended) that would be preserved.

Dinosaurs were a diverse group that were much less constrained in their morphology than the modern crocs and birds that we use as analogues. Birds are remarkable in the reduction of parts from their theropod ancestors (as a weight reducing mechanism for more efficient flight), so we can't expect them to have the same features as their terrestrial precursors. Modern crocs are adapted to a predominately aquatic lifestyle, which again makes it difficult to infer that dinosaurs would deal with the problems of reproduction in the same way. How would the extinct terrestrial crocodillians have mated? Probably with a bigger penis.

Some armadillos have very long penises (about a third of their body length) - if we only compared them to bats and duck-billed platypae would we consider this likely? These comparisons are all within the Mammalia, so why would we expect dinosaurs to be less functionally diverse when comparing them to taxa outside their Class and highly derived, flight-constrained taxa within it?

I expect dinosaurs just had large penis-like apperatus that they used to transfer sperm, we're just too constrained by lack of evidence to say so.

Well there has been a lot of stuff recently about duck 'penises'. Some of these are longer (when extended, obviously) than the body of the duck so certainly at least one dinosaur descendant has manged this feat. It hardly makes it impossible for large dinosaurs to have done the same, and given the sheer body sizes involved may have been essential for large sauropods.

Dear All,

An extensive article was published on this topic in the last issue of Historical Biology.

The socio-sexual behaviour of extant archosaurs: implications for understanding dinosaur behaviour

Author: Timothy E. Isles

Affiliation: Palaeobiology Research Group, School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth, Hampshire, UK

DOI: 10.1080/08912960903450505

Publication Frequency: 4 issues per year

Published in: Historical Biology,
Volume 21,
Issue 3 & 4
September 2009, pages 139 - 214

Dave, not the duck penises again. Surely the most incongrous article in Nature I have seen during my working career...

"Hope is a duty from which palaeontologists are exempt."
David Quammen