Short gap between being a scavenger or predator

I have been sampling once or twice a month this year on Wilcox Ranch, a Solano Land Trust property just a bit south of Dixon. Last night will be the final trip until the rains return in the fall or winter. This property includes a system of vernal pools and is home to the listed Delta Green Ground Beetle (Elaphrus viridis).

Sunset at Wilcox Ranch. The day begins for beetles.

The water is gone from the vernal pools now and only a 2×3 meter puddle remains in the bottom of the man-made levee. After the sun sets, around the last bit of water, many hundreds (maybe in the low thousands) of tiny Bembidion beetles and dozens (probably in the low hundreds) of Chlaenius came out for an end of the season frenzy. There are three species of Chlaenius on the ranch, and the most abundant was the relatively big Chlaenius sericeus viridifrons. The other two, smaller-sized beetles, C. harpalinus and C.¬†variabilipes, are always less abundant.

I have seen many carabids eating all kinds of plant and animal material, but this is the first time I have found a mass of Chlaenius devouring a salamander. Many were engorged, with obvious bloated abdomens. They would tear at the carcass, ripping off a hunk the size of their head and scurry off to a dark crack in the mud to enjoy their meal. Others, with a better position on the body, would stay, eye deep in their meal gnawing and slurping up the juices. Some individuals of the two other Chlaenius species were seen moving furtively around the perimeter, but none made it to the table. Perhaps when the sericeus pack is sated they will feed.

A swarm of Chlaenius sericeus viridifrons gorge on salamander

Seems unlikely that the beetles take on healthy salamanders, but this one was very fresh (it was nearly 38C during the day and that would have dried it out rapidly) and so it may have been weak and so readily finished off. But it is possible that they actually kill them, this behavior is known, and if you haven’t see it check out how some big chlaeniine beetles kill and eat amphibians.

IMG_0403

About 18-20 beetles are on the “kill” or “find.” Also one Agonum fossigerum (upper right) tried to get in on the action. No luck.

During the night of headlamp searching I found five salamander bodies including this one. The other four were dry, had no beetles associated with them and three had been partly to mostly stripped of flesh.

Circumstantial, yes, but perhaps salamander is rather commonly found on the menu. Before the end of the evening I saw a large tiger salamander out walking. I warned him not slow down, the Chlaenius are watching.

 

Predator or scavenger? Image by Nash Turley

The watchful Chlaenius. Predator or scavenger? image by Nash Turley

 

 

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About Kip Will

I'm an insect systematist with expertise in carabid beetles, who is always happiest in the bush.
This entry was posted in Carabids, Coleoptera, Entomology, Pterostichines. Bookmark the permalink.

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