Order - Myliobatiformes
Family - Myliobatidae
Genus - Myliobatis
Species - californica
The bat ray was described in 1865 as Myliobatis californica by Gill. Gill also referred to this species as
Myliobatis californicus and it may have also been referred to as Rhinoptera encenadae Smith 1886.
The common names for Myliobatis californica throughout English-speaking countries is the bat ray and the bat
ray due to pectoral fins that resemble bat wings. Other names include aigle de mer técolette (French), Californische
adelaarsrog (Dutch), raya gavilán (Spanish), raya murciélago (Spanish), and tecolote (Spanish).
The distribution of the bat ray is limited to the eastern Pacific Ocean from Oregon (USA) south to the Gulf of
California and also near the Galapagos Islands (Ecuador).
World distribution map for the bat ray
This ray is found in muddy and sandy bottom bays, rocky bottoms, and kelp forests. Primarily a resident of shallow
waters, the bat ray can be found at depths ranging from 1-46 m either singly or in large schools with members of
their own species or species of eagle rays. It has been hypothesized that diel movement patterns of the bat ray toward
warmer inshore water during cooler times of the day and out to cooler deeper water during warmer hours may be
attributed to behavioral thermoregulation. The bat ray has been reported to jump out of the water and to skim along
the surface for extended periods of time.
Importance to Humans
© George Burgess
- · Distinctive Features
Bat rays have a flat body with a distinct protruding head, large eyes, and smooth skin. The whip-like tail is as long
or longer than the body width with a dorsal fin at the base and armed with a barb-like spine located just behind the body.
This ray is commonly referred to as bat ray, named for its long pectoral fins that resemble bat wings. The bat ray is
easily distinguished from manta rays by the lack of the arm-like cephalic fins that manta rays have on either side of
Bat ray showing the white coloration of the underside
courtesy National Marine Fisheries Service
- · Coloration
The bat ray has smooth skin which is dark brown or black in color, changing to white on the
underside with no other distinct markings.
Bat ray jaw
© Cathleen Bester
Dentition of the bat ray consists of a single elongated medial file and three lateral files of teeth on either side.
The lower tooth plate is flat while the upper plate is convex in shape. The teeth are hexagonal, arranged
in non-termino-lateral positions. These plates are used for crushing and grinding prey.
Bat rays move gracefully through the water using their bat-like pectoral fins
courtesy National Marine Fisheries Service
- ·Size, Age, and Growth
The maximum disc width reported for the bat ray is 6 feet (180 cm) with a maximum weight of close to 200 pounds
(91 kg). At birth, young bat rays have a disc width of approximately 1 foot (.3 m).. Typically, females grow
larger than males, reaching weights of up to 200 pounds (91 kg). Bat rays are known to live at least 23 years.
Males reach maturity at disc widths of approximately 26 inches (67-68 cm) and weights of 10 pounds (5 kg) while females
mature at larger widths than males and weights of at least 50 pounds (23 kg). Age of maturity varies between 5 and 6
years for females and 2 years for males.
Bat rays feed on a variety of invertebrates including oysters
- · Food Habits
The bat ray feeds on bivalves, polychaetes, shrimps, and crabs as well as small bony fishes. A study carried out in
Humboldt Bay, California examined stomach contents of over 500 bat rays with clams being the dominant prey item. This
study also indicated food habits of bat rays change with increase in size with a larger variety of prey as well as larger
prey items consumed by rays with increasing size.
This ray uses its snout to dig invertebrates from sandy bottoms. It also captures food by waving its pectoral fins
rapidly to move sand, exposing hidden prey items. Mollusks are first crushed by the bat ray, the shells spit out
and the soft body tissues eaten. Small fish that would otherwise not be able to access the buried prey quickly consumes
left over food particles.
- · Reproduction
Mating occurs in the spring or summer resulting in birth the following spring or summer. The male finds a suitable
mate, swimming close behind the female with his back touching her underside. There may be repeated attempts at
inserting a clasper into her cloaca until success is reached. During copulation, the pair swims together, moving
their pectoral fins in unison. More than one male may pursue a female, resulting in fights among the males. Female
bat rays form large mating aggregations, blocking females that are immature or that have already mated. Following a
gestation period of 8-12 months, the female enters shallow waters to give birth. The litter size is highly dependent
upon the size of the mother, ranging from 2-12 pups. At birth, the pups are 12-14" inches (30-36 cm) width and each
weigh about 2 pounds (1 kg). Each pup is born tail-first with their pectoral fins rolled over the body.
Sea lions are predators on young bat rays
- · Predators
Sharks including the white shark (Carcharodon carcharias) and sevengill
shark (Notorynchus cepedianus), feed on bat rays. Sea lions consume immature bat rays.
Bat rays readily adapt to captivity and are commonly displayed at public aquarium facilities. Bat rays are sometimes
targeted by sportfishers on heavy tackle with shrimp, clams, or crabs as bait. Although there is no commercial fishery
for this species, it is considered a threat to oyster growers. As a result, oyster growers have been trapping bat rays
for many years to avoid heavy profit losses.
Bat rays pose little threat to humans
courtesy National Marine Fisheries
Danger to Humans
As a non-aggressive marine animal, the bat ray poses little threat to humans. However, care should be taken when
handling these fish due to the venomous spine that is located at the base of the tail.
The bat ray is listed as "Least Concern" with the World Conservation Union (IUCN). The IUCN is a global union
of states, governmental agencies, and non-governmental organizations in a partnership that assesses the
conservation status of species. A status of "Least Concern" is determined when a species does not qualify for
"Critically Endangered", "Endangered", "Vulnerable" or "Near Threatened."