A monarchy is ruling at the zoo for the moment, but its reign will be brief.
Monarch caterpillars and butterflies are thriving at Nature Boardwalk at Lincoln Park Zoo. This is an ideal time to see them in their Chicago home, but don’t wait too long. The monarchs depart for their southern realm in late October.
Monarchs mating at Nature Boardwalk at Lincoln Park Zoo. (Photo courtesy of Joel Pond.)
The state insect of Illinois is quickly identifiable by its distinctive orange and black wings with white dots along the edges. Monarchs have wingspans of 3.5–4 inches and, like all insects, six legs.
While in their caterpillar form monarchs eat milkweed, a native perennial wildflower that grows in abundance around Nature Boardwalk. Milkweed contains a toxic alkaloid substance that monarchs can ingest but which makes them distasteful to many birds and mammals.
A monarch caterpillar feeds on milkweed at Nature Boardwalk at Lincoln Park Zoo.
(Photo courtesy of Joel Pond.)
Host plants are very important for caterpillars, because that’s what they eat. No host plant = no monarch caterpillars = less of a chance to see monarch butterflies. Nature Boardwalk is home to many flowering plants that provide sufficient food sources for many butterfly species.
Monarchs are the one of the few species of butterfly that migrate like birds: south in the winter, north in the spring. Massive colonies numbering in the millions travel more than 3,000 miles—coasting on warm-air currents to conserve energy—to fir tree forests in Mexico where they will hibernate.
No individual monarch, however, actually makes the full round trip on this incredible journey. The last generation during the summer—known as the “Methuselah generation”—lives for about nine months and makes the trip south to over-winter. On their way back north (as far as Canada) they will reproduce and die, and their offspring will finish the trip!
While in Mexico the monarchs are in such great numbers that it’s impossible to count them. Instead, ecologists measure the amount of forest they take up each year, and use this as a metric for how their population is doing. Sadly, it’s been declining.
Habitat destruction and the increased use of genetically modified crops are major causes. Herbicide-resistant crops, for example, allow farmers to spray more and have killed large amounts of milkweed that used to grow between crop rows.
Want to help reverse this trend? Plant milkweed! The monarchs will love you for it.
Mason Fidino is coordinator of wildlife management for Lincoln Park Zoo's Urban Wildlife Institute.