Mane Topics, Vol. 72:3:5, March 30, 1999

The Coevolution of the Monarch Butterfly, Danius plexippus, and the Saber Tooth Lion, Smilodon fatalis.
    by Charles M. Nelson

Rancho La Brea, CA. Palaeontologists and museum officials are meeting with the press this Thursday to reveal the remarkable coevolution of California's official state fossil, Smilodon fatalis, the Saber Tooth Lion, and that other Californian icon, the Monarch butterfly, Danaus plexippus. The third unhappy star of the event is the elephant, who palaeontologists are casting as the "heavy" in this ancient drama. All three are now on view together at a new, in situ museum display built over a portion of the ancient bone bed where the tar pits claimed the lives of so many careless creatures of yore, more than 12,000 years ago.

In defense of Monarchs: Smilodon in action at La Brea - R. Zalinger 1953.


Rudolf (Rudi) Zallinger 1919-1995

This amazing story begins with Rudi Zallinger. In 1950, Rudi created the famous Peabody Museum dinosaur mural that had such a profound influence on the popular mind and mainstream palaeontology. In 1953, Life commissioned a series of works on the Age of Mammals. In due course. these became the mammal mural at the Peabody. The painting above is his original study for summer at the La Brea tar pits, showing Smilodon, the elephant and the Monarch butterflies. These last were removed when the mural was painted due to the absence of fossil evidence of Monarchs at La Brea, a missing link that is now being reported.

Smilodon is well known from Rancho La Brea, where over 2,000 individuals have been recovered and where the bones of Elephants are also abundant. But the star of the new exhibit is the Monarch butterfly, recovered for the first time in its fossil form during ongoing excavations in La Brea's fossil beds.

A Monarch Butterfly fossil recently found in the Rancho La Brea bone bed closely associated with Smilodon fatalis. Here the fossil is photographed using the same special ultraviolet light frequency which has been used so successfully to reveal the soft body parts of dinosaurs. This throws the wing structure and pigment spots into bold relief and even gives some hint of the scale pigmentation between the dark veins in the wings.

The Monarch has the ability to spray a cloud of toxic scales into the nose of any bird which tries to eat it. This ability, we are now told, evolved in part as a defense mechanism against elephants who found butterflies of the Monarch family to be alluring as cat nip is to most cats. Indeed, the trunk of the elephant evolved partly to suck Monarchs out of the boughs of the trees where they congregate. Unfortunately for the Monarch, the elephant's trunk technology evolved more rapidly than the Monarch's biochemical defense mechanism. The development of a migration pattern which congregated Monarchs in a small portion of the elephant's total range was a further adaptation, but only partially effective due to the gluttonous apatite of pachyderms.

Things might have gone badly for the Monarch but for Smilodon, the only natural predator of the elephant. Monarchs learned to light out on water vegetation at the margins of large ponds and lakes, and on the tar ponds of the La Brea. The elephant would come to the edge of the lake, or the tar pit, and stretch out its trunk in an effort to vacuum in a butterfly or two. A bit to close and the butterfly retreats a bit. Just a little further -- just a stretch of the trunk and ... Smilodon fatalis pounces, sinking his enormous sabers into the hapless pachyderm, and the Monarchs fly happily about their business. The elephant became extinct in the Americas as Smilodon gave way to the Mountain Lion, but the Monarchs fly on happily, a living memorial to the king of beasts.