Each hypothetical battle involves guessing what two animals would do if they met face-to-face: would one run away, or one hiss and try to make itself look scary, or yawn and not really care? Whoever quits the field of battle loses, whether they fought the opponent or not. Just look at the pairs of animals in the bracket for Round 1, pick who you think would win out of each pair, and then compare those pairs of winners in Round 2, and pick who would win, and so on until you decide who will win overall (Katie Hinde, who created MMM, has a detailed outline of exactly of the competition works here). In early rounds, the place of battle is in the higher seeded animal's habitat, giving them the home-ground advantage. But be cautious: a higher seeded animal won't always beat a lower seeded animal, because who knows what interesting behaviour or outside event will cause an upset!
The point of MMM is to discuss cool and interesting aspects of mammal biology and behaviour, all the while cheering for your favourite animal to win!
I'm filling out my bracket now, and I'm excited that there is an extinct mammal division this year, called the 'Antecessors'. Here's a brief run-down of the first four pairs in this division and who I'm picking to win Round 1. Check out my second post to see my picks for the rest of the Antecessor division.
Doedicurus vs. Jugulator
Jugulator (not to be confused with the Judas Priest album of the same name) was a predatorial, possibly gliding, early mammal species that lived during the Cretaceous. Although the thought of a predator gliding through the air to pounce on its prey might sound terrifying, it probably only weighed around 750 grams (which is actually huge for an early mammal).
I think Doedicurus's size and armour will (obviously) help it win the day. Although, MMM is known to have upsets where unlikely contestants win...
Cynognathus vs. Thalassocnus
Thalassocnus, on the other hand, was a semi-aquatic, if not fully aquatic, giant marine sloth from the Miocene-Pliocene. It was approximately 2 m long, and although it could walk on land, had dense bones adapted to life in the ocean eating seaweeds.
Thalassocnus may be at a disadvantage battling the wolf-like Cynognathus in the deserts and swamps of Triassic Africa, but with its strong forearms and claws, I think it can defend itself and might just win.
Thylacoleo vs. Procoptodon
Procoptodon was a giant short-faced kangaroo that also lived during the Pleistocene in Australia. They stood between 1-2 m tall (depending on the species) and the largest weighed around 200 kg. Although they may have hopped (as you might expect based on how modern kangaroos move), some new research suggests that they instead walked like other bipedal animals (including humans) do!
If we assume that Thylacoleo was a predator, its sharp teeth and claws could have made quick work of a Procoptodon. Given that they both lived during the Pleistocene and would have encountered each other in the wild, it is possible that Thylacoleo was a specialised hunter of Procoptodon and other large marsupials. Procoptodon could have made a speedy getaway, but only if it could hop instead of walking or running. Hmm... I think I'll choose Thylacoleo to win, but I won't be terribly surprised if this turns out to be an upset.
Andrewsarchus vs. Nuralagus rex
Nuralagus rex was also a giant! But only when compared to modern rabbits and pikas. Like Procoptodon, and unlike modern rabbits, the stiff-backed Nuralagus likely couldn't hop. Coupled with small eyes and ears, it probably couldn't detect or flee from predators very well. Perhaps it didn't need to, as it lived on the island of Menorca during the Miocene that was devoid of large predators.
I feel like this is obvious, but I'm choosing Andrewsarchus to win not only because of its shear size and comparitive power, but also because the isolated island species Nuralagus rex didn't evolve any defence mechanisms against predators.