The Bat Star (Patiria miniata) is a common sea star species found along the Pacific coast of North America, ranging from Alaska down to Baja California. This echinoderm typically features five arms connected by a prominent webbed disk, though individuals can have up to nine arms. They are highly recognizable due to their color variation, appearing in shades of red, orange, yellow, green, purple, or a mottled mix. While primarily a scavenger, the Bat Star also serves as a food source for specialized predators in the marine food web.
Main Animals That Prey on Bat Stars
A relatively short list of animals successfully consumes the adult Bat Star, requiring specialized methods to bypass its defenses. Sea otters are primary predators, as their powerful jaws allow them to crush the Bat Star’s hard skeletal structure. Their ability to manipulate and break open hard-shelled prey makes the sea star vulnerable despite its rigid body.
Certain avian predators, like Western Gulls, target Bat Stars that are exposed in the shallow intertidal zone during low tides. Gulls often swallow smaller sea stars whole, a process that can take several minutes due to the star’s shape and size. While gulls sometimes drop hard-shelled prey like mollusks onto rocks to break them open, the Bat Star is often consumed directly when found, or the gull may peck at the softer underside once the star is overturned.
Other carnivorous sea stars, such as the Sunflower Star (Pycnopodia helianthoides), also prey on Bat Stars. The Sunflower Star is a voracious hunter that uses its numerous arms to quickly envelop and digest other echinoderms and invertebrates. Additionally, larger fish, sharks, crabs, and mollusks are generalist predators that opportunistically consume Bat Stars when encountered.
How Bat Stars Deter Predators
The Bat Star’s primary defense is its physical and chemical composition, making it an unappealing meal to most marine life. Its body is reinforced with a dense endoskeleton made of calcified plates called ossicles, giving the star a tough, rigid texture. This hard, spiny structure makes the Bat Star difficult for non-specialized predators to chew, break apart, or digest.
Many sea stars, including the Bat Star, possess a form of chemical defense by producing distasteful compounds called saponins within their body wall. These chemicals are mildly toxic or simply unpleasant-tasting to most fish and invertebrates, effectively deterring them from predation. This chemical barrier can also manifest as a foul-tasting mucus secreted from the star’s skin, which can trigger an avoidance or escape response in certain predators.
As a last resort, the Bat Star can intentionally shed an arm, a process known as autotomy. This allows the star to escape a predator’s grasp, sacrificing a limb that can be slowly regenerated. The combination of physical armor and chemical deterrence significantly limits the number of animals that actively seek out adult Bat Stars as a primary food source.
Opportunistic Feeding and Scavenging
Bat Star remains provide a food source for a variety of scavengers and opportunistic feeders. Crabs, hermit crabs, and various benthic invertebrates readily consume Bat Star tissue if the animal is dead or severely injured. The remains, along with waste and organic compounds, are quickly recycled back into the ecosystem by this community of scavengers.
A different dynamic exists for the Bat Star’s earliest life stage, the planktonic larva. The adult stars release millions of eggs and sperm into the water column, resulting in microscopic, free-swimming larvae. These larvae are a temporary part of the zooplankton, which are consumed by a vast array of filter feeders and small planktivorous fish. This early life stage mortality represents a major source of loss for the population, as only a small fraction of larvae survive to settle and grow into adult Bat Stars.