Just as an interesting aside,what turned out to be a complete myth that lemmings commit mass suicide was confirmed and was popularised by "the White Wilderness" a 1958 educational Disney nature film in the True-Life Adventure series by James Algar.
The makers had heard stories of Lemmings running off cliffs and so went and found a colony of some 4000 lemmings in Canada and sat down to wait for them to commit mass Hara-Kiri.
After six months the Lemmings were still happily eating and screwing and having a jolly life. Then Agar got a telegram from Uncle Walt asking where his suicidal Lemming movie was. How much longer was he going to have to keep paying for the film crew to do sweet FA other than watch Canadian Rats.
Agar replied he did not know, as the Lemmings seemed perfectly content to inconveniently go on living happy lives.
Agar got an all caps telegram of three words back from Disney stating:
"FIX IT NOW"
So the next day agar hired a 20 man Canadian cleaning crew armed with wide headed brushes, and set up his cameras.
On the command "ACTION" the Canadians began sweeping and driving the entire Lemming colony toward the cliff edge and began shoving them off, to their eternal rest and immortality as Disney movie stars.
Agar filmed it all cleverly keeping the brush men out of shot ... TWICE, before packing up and going back to Disney studios to edit the film and dub in the sounds of voice over artist fake twittering in their best guess at how Lemmings might sound. The actual sound track of terrified rodents and swearing Canucks anciently whacking each other’s shins and being bitten by desperate lemmings running up their trouser legs to escape certain death was though to be not quite the Disney brand.
Some years after Agar and Disney were both dead the children of some of the camera crew and Lemming killers broke the story to accompany the quickly aborted 50th anniversary Re-release of the monster-piece.

Spot on.