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Archaeocetes

2021-02-26 tarasfoundation Dolphins, Ocean Sentinels Club, Science, Whales

Well, we can’t exactly tell you what archaeocetes were, but we can tell you what they were not. They were not filter-feeders like the baleen whales (mysticetes), and they had no form of echolocation, as the toothed whales (odontocetes) do. There are very few clues, but we believe they are not categorized by any unique characteristic.

We know they lived from 50 to 35 million years ago (the eocene period) after which they somewhat abruptly disappeared (geologically speaking, that is). Evidence of their existence has been found in all parts of the world. Archaeocetes probably spent some time on land, and some time in shallow coastal waters, feeding in the tidal zone. There is some debate about whether or not the archaeocetes were the evolutionary predecessor to the odontocetes and mysticetes, but either way there is no doubt that the odontocetes and the mysticetes flourished once the archaeocetes disappeared.

Research has shown that two separate families of cetaceans existed then: the Protocetidae were small-bodied animals, less than 3meters long (9 feet), with their nostrils just behind the tip of their long, slender snout and their teeth not unlike those of a wolf. The Basilosauridae was a medium-sized cetacean, ranging in length from 15-20 meters (45 to 60 feet) in length. This was a rather serpentine animal with un-fused vertebrae, allowing for great mobility in all directions. They had a defined rostrum, but no melon (bulge on the front of their head), and small hind, somewhat useless, legs. They were foragers and lived of fish. It is believed that they hauled themselves out of the water onto beaches to breed, in a way similar to that of seals. The first of these two families disappeared nearly 50 million years ago, and the second family disappeared about 40 million years ago.

Among the archaeocetes were also distinct types of dolphins. Although they were very easily recognized as dolphin in appearance and lifestyle, we would say they both had a very primitive air about them. Both animals were about average in size and used a limited form of echolocation. The Kentriodontids were foragers, similar to the modern-day bottlenose dolphins. The Squalidontids had very long rostrums (beaks) and triangular, serrated teeth (similar to shark teeth). It is believed that they had a very active carnivorous lifestyle, not unlike that of the killer whale. What an interesting appearance they must have had, with their blowhole situated at an odd, forward angle, atop but near the front of their heads. Five or six million years ago both these families disappeared, after sharing the planet for about 25 million years. The reason for their disappearance remains a mystery.

Today, we recognize 14 species of baleen whale including the blue, bowhead, right, humpback, minke and grey whale. Baleen whales are generally larger than toothed whales except for the sperm whale which is very big and has teeth. Depending on the source, tooth whales comprise 69 – 76 species and 6 – 10 families.

The two dolphins most frequently encountered in our study area (off Palm Beach County) are the bottlenose dolphin. And the Atlantic spotted dolphin, both members of the family Delphinidae.

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world.  Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective.  The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

 

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Atlantic Spotted Dolphins -Basic Knowledge

2021-02-21 tarasfoundation Dolphins, Ocean Sentinels Club, Oceans, Science

The Atlantic spotted dolphin is considered playful and acrobatic. They love to ride the bow wave of boats and surf the wake of ships they encounter. They are also more likely to approach humans than other dolphin species and become easily habituated to human activity in the wild, but do not survive in captivity.

PHYSICAL DESCRIPTION
Spotted dolphins are difficult to describe because their size and coloring vary according to their geographic location. Found only in tropical waters, and subtropical waters, there are two recognized species: the Atlantic spe¬cies, Stenella frontalis, and the worldwide species, the pan-tropical spotted dolphin, Stella attenuata. Their long slim beak con¬tains 35 to 48 small conical teeth in each side of the upper jaw and 34 to 47 small, conical teeth in each side of the lower jaw.

COLOR
Spotted dolphins change their coloration as they mature. Newborn calves are dark gray with a white belly (two-tones). As the animal grows older, dark spots begin to appear. First dark spots appear on the lower part of the body (speckled). When sexually mature, light spots begin to appear on the dark upper portion of the body (mottled). Eventually, the spots merge into almost solid color patterns (fused). This color pattern process is a visual indicator of the age of the dolphin.

FINS AND FLUKES
The dorsal (top) fin is tall and curved; the flippers are small and pointed. The flukes are small and pointed at the tips with a small median notch.

LENGTH AND WEIGHT
Length averages about 7 feet (2.1 m); weight averages 220 pounds (100 kg). Calves are 32 to 36 inches (80 to 90 cm) at birth.

FEEDING
Spotted dolphins feed on many varieties of fish and squid found in various water depths. They also feed on small fish and eels found buried in the sand in shallow waters.

MATING AND BREEDING
This species reaches maturity between 6 and 8 years of age or when the animal is about 6.5 feet (2 m) in length. Mating and calving take place throughout the year; the calving interval is believed to be about every 2 – 3 years, but in stressed populations mating takes place at an earlier age and calving at shorter intervals, a response to the enormous mor¬talities suffered from being entangled in nets by the tuna fishery. Gestation is 11 1/2 months and calves are nursed for 11 months. This interval is also longer for male infants, as mothers tend to spend more time caring for the boys. Female calves separate from their mothers earlier and spend a year babysitting the calves of other mothers before becoming mothers themselves.

DISTRIBUTION AND MIGRATION: Atlantic Spotted dolphins are generally found in groups of fewer than 50 individuals but have populations comprising hundreds of animals. These animals are highly social. Schools may contain both sexes and all ages. Some populations are found exclusively in deeper water, some populations prefer to frequent shallow waters, especially for behaviors associated with child care and pregnancy. Atlantic Spotted dolphins are sometimes seen together with bottlenose dolphins.

NATURAL HISTORY
Like all mammals, dolphins are warm blooded, breathe air, give birth to live babies, feed their new born milk, and are born with hair. Being warm, blooded, or homeothermic, dolphins maintain a constant body temperature regardless of the surrounding water temperature. Unlike terrestrial mammals, including humans, dolphins are conscious breathers, mean¬ing they must be aware of their breathing to avoid involuntarily taking a breath while underwater. Atlantic spotted dolphins are capable of diving to up to 60 meters, remaining underwater for up to 6 minutes. They are known to be preyed upon by sharks, but killer whales and other small-toothed whales may also be a threat.
The Atlantic spotted dolphin can often be seen traveling in small pods consisting of up to 15 dolphins. These dolphins enjoy maintaining a high level of social interaction with one another and can often be seen performing leaps and various acrobatic stunts. The Atlantic spotted dolphin communicates using vocal sounds and body language. When it comes to sound these dol¬phins use high-pitched clicks and whistles to communicate about nearby threats, food, a desire to play, and a number of other things. Each dolphin has its own unique frequency which helps them understand who is communicating, and also provides them with a geographic reference (location). This can be extremely useful when a mother for instances needs to keep track of one of her kids or when two friends are communicating with one another in a large pod. Body language is also important for commu¬nication. Dolphins may bump into one another or visualize their body language by spy hopping or leaping out of the water to alert other dolphins of various interests or threats or to display their physical abilities.

THREATS
Spotted dolphins are protected in U.S. waters by the Marine Mammal Protection Act. While the species is not considered endangered, they are, like all marine mammals, exposed to pollutants and biotoxins, and viral outbreaks. Studies of large, high mortality event over the last few decades suggest that the immune system of these animals can be severely affected by heavy metals, PCBs and other pollutants. Atlantic spotted dolphins are not listed as threatened or endangered under the En¬dangered Species Act, and the Western North Atlantic stock is not considered strategic under the Marine Mammal Protection Act. No fishery- related mortality or serious injury has been observed during recent years; therefore, total fishery-related mor¬tality and serious injury can be considered insignificant and approaching the zero mortality and serious injury rate. There are insufficient data to determine the population trends for this species.

We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world.  Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective.  The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

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Bottlenose Dolphins – Basic Knowledge

2021-02-15 tarasfoundation Dolphins, Ocean Sentinels Club, Science

The bottlenose dolphin is the most studied and best known of all cetaceans. This is primarily due to its ready adaptability to captive environment, such as research facilities and marine parks, and its appearance on the TV show Flipper. This dolphin has an extensive range and is the most encountered dolphin species in coastal U.S. waters.

PHYSICAL DESCRIPTION: The bottlenose dolphin has a long and robust body shape, with a pronounced, stubby beak (hence the name ‘bottlenose’), and a distinct melon. Because 5 of the seven neck vertebrae are not fused together as in other dolphin species, the neck of these dolphins is more flexible. They have about 40-48 sharp conical-shaped teeth in both the upper and lower jaw.

COLOR: The color of bottlenose dolphins may range from light to dark lead gray, with lighter shading on the sides, and a white, sometimes pink to pinkish-gray belly.

FINS AND FLUKES: The dorsal fin is triangular, curved and moderate in size, up to 35 cm in height, and located near the middle of the back. The flukes are proportional, curved, with a deep median notch, and are 65-80 cm from tip to tip. Their flippers are pointed and of moderate length.

LENGTH AND WEIGHT: Adult bottlenose dolphins can reach 4 meters (12 feet) in length, and, in some geographical areas, weigh as much as 650 kg (1,430 pounds). However, in most part of the world their weight seems to be limited to about 350 kg (770 pounds). Males are typically larger than females.

FEEDING: These dolphins can be found foraging in deep and very shallow waters. They may hunt and feed individually or in a concerted effort of a group, chasing fish against the water surface, onto mud banks, and shorelines. Association with human fisheries is also reported. They consume about 8-15kg (15-30 pounds) of food each day. Their diet includes a variety of fish species, but also squid and crustaceans.

MATING AND BREEDING: Male bottlenose dolphins reach sexual maturity at age 10, females between 5 and 10 years of age. The gestation period (pregnancy) is 12 months and calves are born in all seasons although in some geographical areas seasonal peaks during spring and fall have been reported. Females give birth once every 3-4 years. At birth, calves acre about 100 cm (3 feet) in length and may weigh around 10 kg (22 pounds). Calves depend on their mother’s milk for 12-18 months but stay with their mother for up to 5 years learning how to catch fish and the social skills to become a full member of dolphin society.

DISTRIBUTION AND MIGRATION: With the exception of polar waters, bottlenose dolphins are found in every ocean around the world, in coastal waters and the open sea. They are frequently encountered in estuaries, lagoons, bays and harbors. There appears to be a coastal and offshore ecotype. Population density appears to be higher in near-shore areas. Bottlenose dolphins are known to have limited home ranges or may be migratory.

NATURAL HISTORY: Like all mammals, dolphins are warm blooded, breathe air, give birth to live babies, feed their new born milk, and are born with hair. Being warm, blooded, or homeothermic, dolphins maintain a constant body temperature regardless of the surrounding water temperature. Unlike terrestrial mammals, including humans, dolphins are conscious breathers, meaning they must be aware of their breathing to avoid involuntarily taking a breath while underwater. Bottlenose dolphins can dive for as long as 20 minutes but typically hold their breath for only 30 seconds to 3 or 4 minutes between breaths.

Bottlenose dolphins may live for 50 years or more, with females generally living longer than males. They live in social communities, sometimes called pods. Group size in near-shore populations is typically 30 or less while offshore groups may comprise several hundred individuals.

Even though they appear to live in relatively open societies, they exhibit strong social bonds that help provide protection against predators, assist in locating and catching food, and aid in the rearing of their offspring. Like in other social animals, play is an important part of learning. Behaviors such as fish toss, bow riding and seaweed-keep-away are considered play but also help dolphins develop social bonds as well as useful hunting techniques. They use multiple feeding strategies, including “fish whacking,” where they strike a fish with their flukes and knock it out of the water, and driving schools of fish into shallow areas or onto mudflats. Bottlenose dolphins use high frequency echolocation to locate and capture prey, and high-pitched ‘whistles’ to communicate with one another.

THREATS: Bottlenose dolphins are protected in U.S. waters by the Marine Mammal Protection Act. While the species is not considered endangered, they are near depletion in some areas and threatened in many others. Incidental and direct exploitation are generally reported at moderate to low levels. According to NOAA, current threats come primarily from incidental injury and mortality from fishing gear (such as gill net, seine, trawl, and long-line commercial and recreational operations), exposure to pollutants and biotoxins, viral outbreaks and direct harvest in some countries (e.g. Japan and Taiwan). Studies of large, high mortality events over the last decades suggest that the immune system of these animals can be severely affected by heavy metals, PCBs and other pollutants.

In an effort to reduce injury and mortality of coastal bottlenose dolphins along the eastern seashore of the U.S., the National Marine Fisheries Service implemented the Bottlenose Dolphin Take Reduction Plan (BDTRP). This initiative includes provisions for research and education, and requires modifications of fishing practices for small, medium, and large-mesh gill-net fisheries from New York to Florida.

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world.  Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective.  The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

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The Face is Familiar, but …

2021-02-01 tarasfoundation Dolphins, Ocean Sentinels Club, Science

 

 

The casual identification of individual cetaceans probably started when humans began interacting with coastal species over a century ago, when whalers and fishermen could identify a few individual killer whales by the shape and coloration of the dorsal fin. This technique, much refined, is still used today.

Scientists, studying cetaceans have long understood and appreciated the need to track individual whales or dolphins. Identifying individuals can help in the collection of information on group composition, site fidelity, movement patterns, population size, as well social structure. Given that dolphins and whales are extremely social animals, understanding the social structure of the population is vital to understanding cetaceans.

Most cetacean studies are conducted from the surface, where the dorsal fin is often the only visible part of the dolphin and therefore the only part usable as an identifier. Luckily, the trailing edge of the dorsal fin, which consists of a thin sheet of flesh and connective tissue, is the most identifying feature of most dolphins and porpoises. Small nicks or larger notches in this area of the dorsal fin are consistent markings that can be used to track individuals over time. However the shading, coloration and overall shape of the dorsal fin can also be helpful.

Some cetaceans have other areas that are more useful as identifiers. The humpback whale has unique markings on the bottom of its flukes, the right whale has large crusty growths on its upper lip that grow in unique patterns and are used to identify individuals and the spotted dolphins have spots; clusters and constellations of spots which are great individual markings and very helpful in the identification process. These dolphins, however, get more and more spots as they develop from infants to adults, identifying spot clusters get covered by new spots, and so it is important to continuously track them over time. All of these identifiers are, in most cases, very subtle, and hard to track in the field. This is where capturing images with photo or video cameras becomes important.

In nearly all studies of cetaceans that track individuals, photo-identification techniques are used to some degree. Most researchers depend on their cameras and photo files a great deal. To get a usable id photo from the surface, it is important to get the dorsal fin on film from a 90-degree angle. This eliminates distortion from angle and helps prevent misidentifications. Any time, we can observe dolphins from underwater, we can use the entire body of the dolphin for identification purposes, which can be very useful, especially in the case of spotted dolphins where we use the spotting pattern across the entire body to identify individual dolphins.

As any field researcher will tell you, it takes a great number of photos to get usable shots. But then, experience does matter and now that we use digital photography, having to throw away bad shots does not hurt as much as it did when we used film.

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world.  Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective.  The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

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