Consider the Bat Ray

Myriobatis californica, the Bat Ray, also commonly referred to as the stingray, is a type of fish classified as a “batoid elasmobranch.” Closely related to sharks, batoids come from an ancient lineage of cartilaginous fishes going back 170 million years. Rays swam through the oceans while dinosaurs walked the earth.

Bat Rays swim by flapping their broad graceful wings and undulating them like a wave, effectively flying underwater. Their long tails help with maneuvering, but seem to primarily exist for defensive purposes as they are armed with a venomous barb. Though potentially dangerous, rays only use their tails in defense, and only when provoked. They are quite gentle and friendly in the vast majority of situations and generally like to mind their own business, which is the business of crushing the shells of their prey with their powerful, grinding plate mouths. As bottom feeders, their mouths face downward while their eyes are on the top of their bodies, which would presumably make it difficult for them to find their food. Evolution has solved this problem by providing them with sensory electroreceptors that can detect the small electric fields created by muscle movements, making them extremely effective at the task of locating their prey.

Bat Rays are present in abundance throughout coastal waters along the Pacific Coast, from Alaska down to Baja. They are a common sight in kelp forests, sloughs, and estuaries- anywhere they can rummage around in the muck and look for crabs, molluscs and small fish. Sometimes they move with purpose, while migrating and gliding in and out on the tides, but their patterns of movement while foraging are quite random. Sometimes they are solitary, and sometimes they are observed in large schools numbering in the hundreds or perhaps even thousands. They are most commonly seen in the warm shallow waters of estuaries between spring and late summer, where they mate and give birth to their pups.

Bat Ray pups are born fully formed, wrapped in their own wings like a little burrito, with a protective sheath around their stingers (protective for the mother, that is). This protective sheath falls off within hours, and they begin swimming and foraging immediately. The way in which Bat Rays mate is also worth describing. They mate while swimming, their undersides clasped together with one of the pair inverted, synchronizing their wing strokes in an impressive display of grace and coordination.

The 1999 Baylands Ecosystem Habitat Goals report categorized the many creatures of San Francisco Bay in the context of where to focus efforts on ecological conservation and restoration. Bat Rays were determined to have the following ecological characteristics:

• Habitat Indicator Species: Bat Rays are highly indicative of a specific type of healthy habitat — namely shallow estuaries and mudflats.
• Dominant Species: Through their behavior, Bat Rays shape and change the environment around them in a way that creates and maintains habitat for other species. This is referred to as being an “ecological engineer.”
• Practical Species: Studying Bat Rays is a practical and effective way to study the broader health of shallow water ecosystems.

When Bat Rays forage in the sand and mud, they vigorously flap their winds, stirring up sediments to expose their prey. This in turn allows much smaller fish to follow behind them and feed on creatures that would otherwise be out of reach and buried in the muck. By constantly kicking up sediments, I would imagine they play an important role in maintaining the underwater topography of subtidal and intertidal zones. Creating habitat for them means treating stormwater runoff from the urban environment to reduce pollutants, which requires green infrastructure improvements on land, thus highlighting the interconnected health of terrestrial and aquatic ecologies. By focusing on the Bat Ray for our “Creature” contest park design in Marin City, we aim to craft the ideal conditions for an ecological engineer that will in turn create and maintain habitat for all of the other species that inhabit shallow lagoon waters.

A significant section of Marin City lies close to sea level, which will be steadily rising in the decades to come. The lagoon will eventually, inevitably expand in size. While this reality is cause for worry, it is also a call to action and adaptation, and an opportunity for the restoration of historical intertidal wetlands. By focusing on the Bat Ray for this “creature” competition, we hope to tell a story where adaptation is not just a forced reaction, but rather a creative decision made to embrace coastal inundation and recreate our communities as part of a “blue green system” that can rise and fall on the tides, where the interface between humans and nature is accepted as diffuse and porous. Bat Rays, ecological engineers extraordinaire and graceful prehistoric beasts of the sea, can be our friends and allies in this creative effort.