First off, let's eliminate some confusion on the topic.

Although the terms "dolphin" and "porpoise" are often used interchangeably, these marine mammals, in fact, belong to two distinct scientific families (dolphins: Delphinidae / porpoises: Phocoenidae), and porpoises are not found naturally in Gulf waters (or the coastal waters of bordering states). The main differences between the two are that porpoises have spade-shaped teeth, no beak, and a triangular dorsal fin (when they have one); dolphins have cone-shaped teeth, usually a beak, and a hooked or curved dorsal fin (when they have one). To put it in perspective, dolphins are about as closely related to porpoises as redfish are to cobia.(1)

So that porpoise that ate half the fish you were reeling in? Definitely a dolphin. Actually, in this respect, fishing around dolphins is similar to fishing around sharks or barracudas. At some point, you might lose a catch to their appetite, though this happens infrequently with dolphins as sharks are much more often the culprit of stolen catches. Dolphins will also frequently follow commercial fishing vessels to prey on unwanted catch that is discarded or fish protruding from the nets while they are still in the water. They'll tolerate high levels of disturbance, noise, and pollution for the advantage of an easy food supply.(2) However, our similar tastes in seafood often lands dolphins on the wrong side of the net. All cetaceans (whales, dolphins, and porpoises) are protected in the U.S. from hunting and poor commercial fishing techniques by the Marine Mammal Protection Act (MMPA), but this doesn't protect them completely from incidental take.(3) Dolphins are caught in a variety of fishing gear, including gill nets, purse seines used for tuna catch, and shrimp trawls. They are also vulnerable to pollution, habitat alteration, petroleum resource development, boat collisions, and other human disturbances (such as feeding and swimming with).(4) Though dolphins do, on occasion, appear friendly and inviting to swimmers and boaters, it is important to have as little interaction as possible. Besides being illegal to feed, touch, harass, or harm wild dolphins, excessive human contact can cause wild dolphins to lose some of their natural wariness needed for survival. Plus, dolphins in the wild do bite! They can be unpredictable and aggressive, just like any other wild animal. (1)

An unusual habit among cetaceans that can occur as a result of negative human impact or natural causes is stranding, when a dolphin (or whale, or porpoise) beaches itself out of water, without the ability to return under its own power. It's unclear as to why all strandings occur, but possible causes include parasites, disease, choking on ingested objects, wounds from gunshots or boat encounters, difficulties in birth, starvation, pollution, net entanglements, misfunctioning sonar, and panic.(1)

Of the numerous species of whales and dolphins noted on the Texas coast, the bottlenose dolphin is by far the most common. This is a relatively robust dolphin with a comparatively short beak and a sleek, streamlined body. The skin is smooth and rubbery. Coloration varies somewhat: the top can range from pale gray to slate gray with tinges of green, brown, or purple; sides fade down into a white, pinkish-white, or light gray underside. There are 40-52 sharp, conical teeth in the upper jaw, 36-48 in the bottom. Bottlenose dolphins have more flexibility in their necks than other oceanic dolphins because five of the seven neck vertebrae are not fused together as in the other oceanics. Adults grow from ten to thirteen feet, males being larger than females, and average life expectancy is twenty-five years, though they have been known to reach fifty.(4)

Female bottlenose dolphins seem to be sexually receptive most of the year and often initiate the courtship and breeding behaviors. Just before mating, a male will rub the female and may exhibit an "S-curve" posture, head lifted and tail flukes pointed down. Though they can breed year round, data suggest that in Texas waters, peak breeding occurs from March to May, which is also the peak time for calving since gestation is a year. Females give birth to a single calf (multiple births being very rare) every two to three years. A newborn calf ranges from three to four feet, a third or more as long as its mother, and is usually born tail first to prevent drowning.(3) Birth may be assisted by an "auntie" dolphin, though it may be male or female, and this dolphin is the only one allowed near mother and calf. Studies suggest that, like humans, there's much learning involved in motherhood.

Calves are darker than adults, and newborns sport several vertical, light-colored lines on their sides as a result of fetal folding. These lines disappear within six months. A mother whistles continuously to her calf for several days after birth. This acoustic imprinting teaches the calf to identify its mother. Calves nurse up to eighteen months but will stay with their mothers three to six years, learning how to be dolphins. Females sexually mature at about 7.5 feet (five to twelve years); males mature at 8-8.5 feet (ten to twelve years).(5)

Bottlenose dolphins are active predators and eat a wide variety of fishes, squids, and crustaceans, though mullet constitutes a large part of their diet in Texas bays.(6) Feeding usually peaks in early morning and late afternoon, and throughout the course of the day, an adult eats approximately four to five percent of its body weight, about forty to eighty pounds. Prey is swallowed whole or torn into swallowable chunks. There are several hunting strategies. Individually, a bottlenose may slap a fish out of the water with its tail to stun it, dig in the sand for hidden prey (located by the dolphin's trusty sonar), snap up bycatch from fishing boats, or even lunge onto shoals and sandbars in pursuit of a panicked fish. Often they hunt in groups, pressing schools of fish into tight balls and taking turns zipping through or herding them into the shallow waters of a sand bar for easy pickings.(5) During winter, bottlenoses seem to prefer hunting in coastal Gulf waters or deep-water passes (shipping channels and such) while in the summer, they feed often in shallow seagrass habitat. (2)

Occasionally, bottlenoses are someone else's dinner. Their predators include tiger sharks, dusky sharks, bull sharks, and very rarely, orcas. An individual dolphin is less likely to succumb to this fate if he or she is part of a pod, the coherent long-term social groups dolphins form. Pods in Texas waters generally consist of two to fifteen bottlenoses, though in the Gulf, pods may merge to form herds of several hundred individuals. Pod size is affected by habitat structure and tends to increase with water depth and openness. Composition is based largely on age, sex, and familial bonds. Dolphins are highly social with each other: cooperating in feeding, protective duties, and nursery activities (even so far as calf baby sitting).(6) Communication comes in varied forms: squeaks, whistles, body language (including leaps as high as twenty feet in the air), jaw snapping, tail slapping, and head butting, just to name a few. They alert each other to danger, point out the hot spots for food, and even work as scouts for the rest of the pod by investigating novel objects or unfamiliar territory.(7) There may be social hierarchy among the individuals of a pod. Dolphins show aggression by blowing bubbles from their blowholes, biting, or dragging their teeth along another's skin. Bottlenoses may aid an injured pod mate by vocalizing or physically supporting the dolphin. Each dolphin has its own signature whistle, its name, you might say. All ages of bottlenoses will chase each other, carry objects around, toss seaweed or fish to each other, use "toys" to garner attention... Some of this activity may be training or practice to catch food, but no one really knows what's going through their minds. Bottlenose dolphins have larger brains than humans, but the section concerning intelligence is smaller.

Probably the most well-known dolphin sense is echolocation, high frequency clicks, whistles, barks, groans, trills, grunts, squeaks, etc., which act as the dolphin's sonar. Through echolocation, a dolphin can decipher the shape, size, speed, distance, direction, and even some of the internal structure of an object in the water.(7) These noises serve a dual purpose of communication and navigation. It is theorized that most of the dolphin's vocalizations originate in the nasal sac (dolphins lack vocal cords). As might be expected of an animal using echolocation, dolphins have phenomenal hearing, twice as many auditory nerve fibers as humans. But something's amiss: they don't hear through their ears! (Or not very much anyway; there is some debate among scientists as to how much.) Most of the sound reception takes place in the lower jaw. A fat-filled cavity in the lower jawbone conducts sound waves to the middle ear (not readily connected to the outer ear), inner ear, and on to the auditory nerve. This method of hearing is more effective for localizing sounds under water. As for their other senses: good eyesight with possible color reception, sensitive to touch, very limited smelling capacity (no olfactory nerves), taste unknown, though they do possess taste buds and fish preferences.(5) They generally will hold their breath for eight to ten minutes at a time.

Bottlenose dolphins are commonly seen in bays, estuaries, and ship channels but are certainly not limited to Texas waters or even the Gulf. They're found worldwide in tropical and temperate areas (no cold waters, please). Though only one species of bottlenose is recognized, there seem to be two ecotypes (forms): the coastal ecotype, adapted for warm, shallow waters with a smaller body and larger flippers to dissipate heat, and the offshore ecotype, with blood qualities better suited for deep diving and a larger body to conserve heat.(3)

The second most common dolphin in the Gulf is the Atlantic spotted dolphin. As the name suggests, it doesn't get around quite as much as the bottlenose. Much of what we've covered with the bottlenose dolphin also applies to the Atlantic spotted, so we'll just cover the differences, starting with looks.

The Atlantic spotted dolphin, also called the Gulf Stream dolphin, is rather small (5-7.5 feet), chunky, long-beaked, and, well, spotted. In general, they go through five color phases: 1) newborn calves are dark gray with a white belly and NO spots, 2) color divides: dark top, light belly, still no spots, 3) dark spots begin appearing on belly and lower sides, about four years old, 4) light spots appear on top and upper sides, and 5) dark underside spots merge into almost a solid color near the tail, with pink shading near the forward part of the belly. Throughout, the beak is black except for white lips and a white tip; both eyes are circled in black with a connecting black line across the beak. The older a dolphin, the more spots it has. The dorsal fin is tall and curved; the flippers are small and pointed. They have almost twice as many teeth as bottlenose dolphins.(4)

The social behaviors are similar to bottlenose dolphins, including a pod hierarchy, whistled communications, baby sitting, etc. In fact, sometimes pods of both species will join up. Breeding/calving occurs in the same season. Sexual maturity is reached between six and eight years of age, or about 6.5 feet in length. Gestation is about twelve months; calves nurse for eleven months, and moms give birth every two or three years. Sound familiar?(4) Hunting strategies can be individual or group oriented, and food preferences range from small fishes (such as herring, anchovies, and flounder) to squid, eels, octopi, and crustaceans.

Echolocation, hearing, and other senses all comparable to bottlenoses (and generally speaking, across the Delphinidae family). Atlantic spotteds are often described as acrobatic swimmers due to their frequent breaching (jumping out of the water and landing on their sides or backs), leaping, and other aerial activities. They are capable of very fast swimming and commonly approach ships to bow ride (riding the bow pressure waves of a boat).(8) Their dives generally last six to eight minutes. This particular species of dolphin is very timid, though they have been known to approach humans in the Bahamas.

Both bottlenose and Atlantic spotted dolphins have a position of apex predators in their ecosystems, a position shared by most of their cetacean cousins. They keep their prey populations in check, and since they often feed on the old and sick, they also keep the prey populations healthy. In addition, bottlenoses may turn out to be a good indicator species, a species that embodies or magnifies the characteristics of a particular region. An indicator species can be sensitive to one or more variables of interest, such as salinity, pollution, extreme conditions, etc. Since bottlenose dolphins have a diverse prey base, they concentrate contaminants in their bodies when there are high concentrations of contaminants in the water, and therefore are a good indicator of pollution levels.

As always, despite whatever annoying or endearing qualities we find in these animals, they, too, have their specific niche to fill in the ecosystem, keeping it productively status quo.

Where I learned about dolphins, and you can too!

(1) "Frequently Asked Questions," Texas Marine Mammal Stranding Network, 25 September 2011 <>.

(2) K. S. Maze and B. Wrsig, "Bottlenose dolphins of San Luis Pass, Texas: Occurrence patterns, site-fidelity, and habitat use," (Texas A&M University at Galveston, Marine Mammal Research Program: 1999).

(3) "Bottlenose Dolphin" & "Atlantic Spotted Dolphin," The Mammals of Texas - Online Addition, 25 September 2011 <> & <>.

(4) "Bottlenose Dolphin" & "Spotted Dolphin," American Cetacean Society, 26 September 2011 <> & <>.

(5) "Bottlenose Dolphins," SeaWorld Education Department, 26 September 2011 <>.

(6) "Bottlenose Dolphin (Tursiops truncatus)," Texas Parks & Wildlife Department, 25 September 2011 <>.

(7) "Creature Features: Bottlenose Dolphins," National Geographic Kids, 25 September 2011 <>

(8) "Atlantic Spotted Dolphin (Stenella frontalis)," NOAA Fisheries: Office of Protected Resources, 26 September 2011 <>.