Any animals that mutually kill each other?

[Ludovic]

It seems that in nearly every inter-species relationship it is one of the species that does most of the killing, if at all.

Is there any pair of multicelled species that kill each other on a regular basis and whose death rates are reasonably equal, at least around 20%/80% (ignoring the few times that a prey kills a predator with a stomp, for instance)?

[Autolycus]

I'm not sure if this is true or not, but I recall hearing that in Africa, hippos and crocodiles fight each other on a daily basis and that the outcome is about 50-50.

[Myron Van Horowitzski]

Obligatory image (http://cellar.org/iotd.php?threadid=9308).

[Zsofia]

What about sperm whales and giant squid? I guess there's no way to get statistics on them.

[yabob]

Lions and hyenas. The lion probably has the edge, but the hyenas win sometimes, usually when they gang up on an individual lion.

[The Great Sun Jester]

Obligatory image (http://cellar.org/iotd.php?threadid=9308).
Niiiiiice. Took me a year to get that out of my head the first time.

[flight]

Do they both have to be adults? There are many species that will eat each others' young, or rolls reverse once they mature.

Think of cute little Sugar Gliders eating Kookaburra eggs and then kookarburras eating the Sugar Gliders.

[robby]

Cobras and mongooses.

They're both predators that would be happy to have the other for a meal.

[Hello Again]

I saw on a nature channel that cape buffalo are extremely dangerous and can kill a full grown lion, although the lions do continue to hunt them.

[awldune]

What about sperm whales and giant squid? I guess there's no way to get statistics on them.

It's my understanding that squid don't stand much of a chance, although they do leave nasty scars. I saw a show about giant squid recently where they showed 10-15 squid beaks from the stomach of a single whale. ISTR that this was a typical number, so a 20%/80% ratio is unlikely.

[The Great Sun Jester]

...squid beaks
Band Name!!!

[chowder]

Humans