What Predators Help Control 13-Year Periodical Cicada Populations?

Periodical cicadas are one of the most fascinating and enigmatic insects found in North America, renowned for their unique life cycle and synchronized mass emergences every 13 or 17 years. Among these, the 13-year periodical cicadas, belonging to the genus Magicicada, are particularly intriguing due to their predictable yet infrequent appearances. While their sheer numbers during emergence can seem overwhelming, a variety of predators play crucial roles in controlling their populations and maintaining ecological balance. This article explores the key predators that help regulate 13-year periodical cicada populations, shedding light on the intricate predator-prey dynamics in these episodic natural events.

Understanding 13-Year Periodical Cicadas

Before diving into predation, it’s important to briefly understand what makes 13-year periodical cicadas unique:

• Life Cycle: These insects spend most of their lives underground as nymphs, feeding on xylem fluids from tree roots. After 13 years, they emerge en masse to molt into winged adults.
• Mass Emergence: The synchronized emergence, sometimes numbering in the millions per acre, happens over a few weeks in late spring or early summer.
• Reproductive Strategy: They mate, lay eggs, and die within a few weeks above ground, after which their offspring burrow underground for another 13 years.

This extraordinary life history not only fascinates scientists but also creates a buffet for many predators that rely on this cyclical bonanza.

Why Predators Matter for Cicada Populations

Despite the massive numbers during emergences, periodical cicadas avoid extinction mainly through a strategy called predator satiation. By emerging in overwhelming numbers, they essentially satiate predators so that many individuals survive to reproduce. However, predation still significantly impacts local population densities and influences cicada behavior and evolution.

Predators help:

• Keep cicada populations in check to prevent damage to host trees.
• Maintain food web balance by providing a rich food source during emergence years.
• Influence cicada emergence timing and aggregation patterns through selective pressures.

Now let’s explore some of the key predators involved in controlling 13-year periodical cicada populations.

Avian Predators: Birds on the Hunt

Birds are among the most visible and voracious predators of periodical cicadas. Their ability to fly and keen eyesight make them highly effective at locating and consuming large numbers of these insects during emergence.

Common Bird Predators

• American Crow (Corvus brachyrhynchos)
  Crows are opportunistic feeders known to take advantage of cicada emergences. They can consume dozens of cicadas daily and have been observed caching excess food.

• Blue Jay (Cyanocitta cristata)
  Blue Jays are agile foragers with strong bills capable of breaking through cicada exoskeletons.

• Gray Catbird (Dumetella carolinensis)
  These birds feed on both adult cicadas and freshly hatched nymphs before they burrow underground.

• Northern Cardinal (Cardinalis cardinalis)
  Cardinals pick cicadas off leaves and branches, feeding on both adults and remnants.

• Red-tailed Hawk (Buteo jamaicensis)
  Although primarily hunting small mammals, these hawks take advantage of large flocks of emerging cicadas as an easy meal.

Impact of Birds on Cicada Populations

Bird predation can reduce adult cicada density locally by significant percentages. Studies show that birds consume hundreds to thousands of cicadas per day during peak emergence periods, which helps reduce potential damage caused by egg-laying females on tree branches.

Mammalian Predators: From Small Rodents to Larger Carnivores

Mammals also play an important role in preying upon periodical cicadas. Their diverse feeding habits allow them to exploit both adult cicadas and nymphs.

Small Mammals

• Squirrels (e.g., Eastern Gray Squirrel Sciurus carolinensis)
  Squirrels consume adult cicadas during emergence, often climbing trees to catch them mid-flight or picking them from leaves.

• Raccoons (Procyon lotor)
  Raccoons forage both above ground for adults and dig underground for nymphs.

• Mice (e.g., White-footed Mouse Peromyscus leucopus)
  Mice are known to consume nymphs underground before they emerge, impacting juvenile population sizes.

Larger Mammals

While less common, larger carnivores such as foxes or skunks may opportunistically feed on adult cicadas or dig out nymphs after heavy rainfalls when soil is loose.

Role in Population Control

Small mammal predation tends to be more continuous than avian predation since they can access nymphs underground between emergences. This predation helps moderate baseline population levels prior to mass emergence events.

Reptilian and Amphibian Predators

Reptiles and amphibians also take advantage of the seasonal abundance of cicadas.

• Frogs and Toads (e.g., American Toad Anaxyrus americanus)
  Known for their insectivorous diets, these amphibians feed on freshly emerged adults resting near water or foliage.

• Lizards (e.g., Five-lined Skink Plestiodon fasciatus)
  Lizards hunt adult cicadas basking on tree trunks or leaves.

• Snakes (e.g., Eastern Garter Snake Thamnophis sirtalis)
  Some snakes prey on immature nymphs underground or adults resting during daylight hours.

While reptiles and amphibians may not consume as many cicadas as birds or mammals during peak periods, they contribute to reducing individual survival rates especially within localized habitats.

Invertebrate Predators: Nature’s Tiny Hunters

Predatory insects and arachnids also take part in controlling periodical cicada populations:

Spiders

Orb-weaver spiders build webs near trees where adult cicadas fly and become trapped. They provide an efficient way to capture multiple individuals during emergence peaks.

Praying Mantises (Mantodea species)

Mantises actively hunt adult cicadas using their strong forelegs to grasp prey mid-air or from branches.

Ants (Formicidae)

Ant colonies exploit fallen dead or weakened adult cicadas but can also attack vulnerable nymphs near the soil surface after rain events.

Wasps

Certain wasp species hunt cicadas directly or parasitize them:

• Cicada Killer Wasps (Sphecius speciosus)
  These large wasps specialize in hunting adult cicadas as prey for their larvae.

• Parasitic Wasps (family Encyrtidae and others)
  Lay eggs inside eggs or young nymphs, reducing viable offspring.

Though smaller individually than vertebrate predators, cumulative predation by invertebrates is ecologically significant due to their numbers and reproductive rates.

Microbial and Fungal Pathogens: Invisible Population Checkers

Beyond visible predators, microbial pathogens play a subtle yet important role in controlling periodical cicada populations:

• Entomopathogenic Fungi (e.g., Massospora species)
  These fungi infect adult cicadas causing debilitating disease that reduces reproduction.

• Bacterial Infections

Certain soil bacteria infect nymphs underground leading to mortality before emergence.

These pathogens help limit outbreaks by reducing survival rates during vulnerable life stages.

Predator Satiation vs. Predator Impact: A Delicate Balance

The evolutionary strategy of synchronized mass emergence aims at overwhelming predators so many individuals survive despite heavy predation. However, even with predator satiation, predation pressure remains significant:

• Predators reduce overall numbers enough to prevent unsustainable population explosions.
• This balance allows Magicicada species to persist over millennia without exhausting resources or causing excessive harm to host trees.
• Predator pressure may influence emerging timing or behavior changes across generations.

Understanding this dynamic showcases nature’s intricate balance shaped through evolution over countless cycles.

Conclusion

The spectacular emergence of 13-year periodical cicadas may seem like a natural event beyond control due to sheer numbers; however, a diverse cast of predators plays essential roles in regulating these populations:

• Birds such as crows and jays consume vast quantities of adults.
• Mammals including squirrels and raccoons prey on adults and nymphs alike.
• Reptiles and amphibians opportunistically feed on vulnerable individuals.
• Invertebrates such as spiders, mantises, wasps, ants, and microbial pathogens attack various life stages from eggs through adulthood.

Together, this complex web of predation ensures that periodical cicada populations remain balanced within ecosystems. Far from being pestilent invaders immune to natural checks, they participate in an age-old ecological dance with their many predators , a dance that sustains biodiversity and ecosystem health across North America’s forests every thirteen years.

References available upon request.