The Monarch Effect: Surviving Poison, Predators, and People

Although monarch caterpillars are little eating machines, they do have one other important job: to not be eaten! How do they defend themselves against the flies and wasps that try to make them their meal? Interestingly, monarch caterpillars react to sounds, and they react to the buzzing of a predator’s wings as it approaches. The caterpillar freezes, ducks or twitches its head up and down, waves the two antennae-like filaments on its head (called tentacles), or even drops off the plant. Freezing is thought to be helpful because some insect predators can zero in on their prey only if it is moving. Ducking, twitching or waving their head shoos the predator away, and dropping off the plant is a quick escape.

Review:

The journey that is a major part of the Monarch butterfly’s life cycle is one of nature’s most amazing migration stories. The overwintering destination in Mexico was shrouded in mystery until 1975. Due to the persistence of scientists, the main site in the state of Michoacán was finally revealed. It had been known to local villagers for several decades, but others were not curious about the butterflies at that time. This book is a close examination of what led to that discovery, and the subsequent advances in studying Monarchs that have enhanced conservation efforts for this colorful insect.

A detailed description of the life cycle of the Monarch focuses on their total reliance on milkweed as egg hatchery and nursery for the caterpillar and on the poisonous cardenolides that make them unattractive to predators such as birds. Several chapters cover the scientists who used various tracking devices and local information to discover the migration sites, and how rivalries among them complicated the scientific research. The next big question was how Monarchs were able to make the lengthy return migration trip all the way from Mexico to the United States and southern Canada each spring. Eventually, it was learned that successive generations of Monarchs made repopulation in the north possible.

That knowledge continued to fuel curiosity about these insects. Citizen Science has played a major role in collecting data on adult butterflies, through organizations like Monarch Watch and Journey North. The Monarch Larva Monitoring Project has delved into studying the eggs and larvae for details on habitat factors such as milkweed, herbicide use and climate change. Advances in tracking methods—e.g. radio telemetry—has helped scientists discover preferred locations for egg laying so that milkweed supply can be protected or enhanced. Animal cognition – the study of how nonhuman animals think, learn, remember and make decisions – has led to experiments in sight, smell and even colour preferences. Monarchs are found around the world, and there is debate over whether they should be listed as endangered. In North America, reasons for decline include forest degradation, changes to habitat, elimination of milkweed by pesticides and herbicides, climate change and wildfire.

A final chapter talks about the cultural significance of Monarchs. Indigenous celebrations, like Día de los Muertos (Day of the Dead), have long exalted the butterflies as souls of lost loved ones returning to the earth, or they can predict a good harvest. The overwintering sites where the majority of Monarchs congregate were designated the Monarch Butterfly Biosphere Reserve in 2000 and a UNESCO World Heritage Site in 2008. Conservation efforts continue to ensure that indigenous knowledge is linked with Western science.

The extensive research that went into this complex story is evident in the detail and in the lengthy reference pages included. The reading level varies, making the target audience somewhat uneven. Life cycle information will be accessible to middle grade readers, but the complexities of the scientists’ rivalries seems more suited to an older audience. Likewise, tracking methods would interest younger readers while the chapter outlining experiments with animal cognition might be more challenging. The choice of black and white photographs is puzzling: for an insect known for its brilliant colors, they have little impact. The picture on page 30 of a winter roost of countless Monarchs is ineffective, resembling only bark or leaves. The design of the book—a 300 page volume that relies mainly on a text-book style presentation--should work for young adults or older readers.

The Monarch story is fascinating, especially due to the mystery of the migration and the lengthy process to make it known to the world. The Monarch Effect shines a light on the need for conservation on many levels for this colourful, fragile insect so familiar to all ages.