In the vast ocean, all creatures are vulnerable. Bottlenose dolphins are cetaceans that rarely become prey, thanks to their size, their intelligence, the use of echolocation and their level of socialization that gives them a significant advantage by staying in groups and intimidating their opponent. However, two predators will take the smallest opportunities to feed on dolphins: killer whales and sharks.

We know that the killer whales are expert hunters, especially when they hunt in organized groups. Although there are few documented cases, these animals that are the world’s largest dolphins, attack other species of smaller dolphins, mainly young, newborn or sick. To do it they separate the mother from the calf, making impossible to the latter defend its offspring.

However, a group of orcas does not feel intimidated by a large pod of dolphins. Although there are no records of this kind of attack to bottlenose dolphins, there are videos where a pod of killer whales approaches aggressively to groups of dolphins of other species, and as if they were seals, they beat them and throw them into the air until they are stunned and finally feed on them. Several types of dolphins suffer this kind of aggression, and the bottlenose dolphins are likely part of this list.

Regarding sharks, the most dangerous species for members of the genus Tursiops are the largest: tiger shark, sand shark, bull shark and, of course, the great white shark. It is not uncommon to observe dolphins with scars from shark attacks, which means they are not easy prey and their escape techniques often help them survive.

A study conducted in Shark Bay, Western Australia, revealed that 95 of 128 bottlenose dolphins analyzed showed scars from shark bites, mostly from tiger sharks. The frequency of new body marks and the high attack rates suggest that bottlenose dolphins are at risk in this locality more than in other parts of the world.

A few cases with rays are known. Although they are not dolphin predators because they have a diet based on small fish, mollusks, and plankton, the trauma and infections they cause with the sharp edges of their tail sometimes become deadly.

Dolphins are active predators that have a carnivorous diet. Their eating habits are flexible so that they can adapt perfectly to the habitat where they live.

Although they have small teeth, they do not use them to chew the food but only to hold the prey. What they do is, once the prey is in their control firmly hold by those teeth, they swallow it whole starting with the head. If the prey is a large animal, then they tear it by shaking or crushing their body so that it breaks into smaller pieces.

The stomach of these cetaceans has several compartments that make digestion a quick process. The daily total food intake varies according to the species, but they do not feed abundantly. For example, a bottlenose dolphin (Tursiops truncatus) consumes between 4 and 5 percent of its weight per day.

Dolphins spend plenty of time finding food every day, and some species can consume up to 30 pounds of fish per day as adults. They migrate and move long distances to find food, although if they have enough supply where they reside, and the temperature of the water is also acceptable, they probably won’t migrate.

Dolphins do not use their teeth to chew the food but only to hold the prey.

FAVORITE PREY

They consume a variety of bony fish, crustaceans, and cephalopods. Individuals living near the coast regularly feed on fish and benthic invertebrates, while those who stay in high seas prefer to eat squid and fish as well.

Specifically, their favorite prey includes:
– Atlantic mackerel
– Herring
– Mullet
– Cod
– Squid
– Octopus
– Shrimp

Orcas (Orcinus orca) are a separate case because their diet includes more than small fish. They are used to hunt other marine mammals such as walruses, sea lions, and seals, as well as penguins, sea birds, and even small baleen whales.

Some reports indicate that deep-sea fish remains have been found in the stomach of some dolphins, pointing out that they may be able to dive up to 500 meters deep to search for food.

HUNTING METHODS

Dolphins use various strategies to catch their food, but they are usually related to group hunting:

HERDING.

When a pod of these cetaceans locates a school of fish large enough, they start to surround their prey to reduce the area of ​​dispersion. Imagine a compact group of thousands of fish going from side to side to avoid a set of predators. When the prey is already disoriented, the dolphins take turns entering the fish school from below and begin feeding themselves. Some others stay on the outer perimeter to avoid the fish to disperse.

Herding is one of the most common methods of feeding that they use; This involves a pod working as a unit to get a school of fish to curl up into a tight ball. Then, they take turns to rush through and plow the center of that ball, eating all they can in the process.

CORRALING.

Other times, a pod goes to the coasts or the sandbanks to facilitate their task as these areas offer a great variety of fish and it is easier to catch them. Dolphins sometimes corral fish in shallow waters so they cannot escape.

Dolphins learned to feed following fishing vessels. Bottlenose dolphins are the species that practices this more often, and it involves following trawl nets to feed on discarded fish and or those thrown back into the water by the fishers.

They do not always hunt in groups. If necessary, dolphins also look for food individually. Orcas and other species herd their prey to the coasts or places where they will not escape and sometimes wait patiently until the victim makes a mistake and can catch them. There are some videos of orcas practically getting half of their body on the sand to the catch seals that feel safe in the seashore, in a move that has to be perfectly coordinated with the ocean waves.

Sometimes dolphins beat the prey with their tails until they come out of the water and they catch them in the air with their mouths.

Recently a particular behavior was discovered in bottlenose dolphins that inhabit the west of Australia: when looking for food in rocky areas, females protect their snout using a marine sponge; Just when they intend to swallow the prey they release the sponge and eat. This unusual but sophisticated behavior is exclusive to females and their offspring.

OTHER DOLPHIN FEEDING METHODS.

The concept of cooperative feeding involves driving the schools of fish to the shallow areas of the water. Sometimes, this is to the coast, or it could be to some natural barrier or even a subgroup of the dolphins making such function. Other species drive prey into muddy banks so that they can simply catch them.

There are certain species of dolphins that use their flukes to stun their prey hitting them, and while the victims are still disoriented, they will feed on them.

What is fascinating too is that in some locations the dolphins have learned to help the fishermen drive the fish into their nets. The payoff for dolphins is that they get to feed on the leftover fish that get out of the nets.

Large pods use circular cooperative feeding. They divide into subgroups and then form circles surrounding schools of fish this way and continue to reduce the overall size of that circle before they take part in consuming them.

Something very similar is the crossing cooperative feeding; This involves dolphins moving in a cross pattern with groups of them swimming in different directions, allowing the fish to be in the middle of the routes that dolphins have created. Such strategy is usually a good one to use around rocky shores and in shallow areas of small bays.

Dolphins are intelligent, so they have the option to create different methods that fit their feeding needs. They have been seen mixing two or more of the mentioned feeding strategies into one session to get results. The ability to create such variations with ease and to build new formations is fascinating. The level of cooperation it takes among the dolphins in the pod is also noted.

FEEDING DOLPHINS?

When meeting dolphins, either in aquariums or in areas that these cetaceans visit, humans can provide them with food, but this action is not good for them.

Researchers point out that the fact that dolphins get quickly accustomed to being fed causing them to lose their natural hunting ability. If you visit an area with ​​dolphins, do not feed them!

References

bioexpedition.com/dolphin-feeding/

Animals, a visual encyclopedia. Smithsonian. Dorling Kindersley, 2012.

Alan Rauch. Dolphin. Reaktion Books, 2013

https://en.wikipedia.org/wiki/Dolphin#Feeding

]]> https://www.dolphins-world.com/fishermen-get-help-capturing-fish-from-dolphins/ Wed, 23 Apr 2014 19:29:51 +0000 http://www.dolphins-world.com/?p=2069 Fishermen and Dolphins

Commercial fishing can be a risky business, but not when you have the right members on your team! In some locations, fishermen are getting help from self-trained Bottlenose Dolphins! This is a winning outcome for the dolphins as well as for the fishermen that are reaping such rewards. What is really interesting in this study in Brazil is that the dolphins were never formally trained for such an outcome.

What has occurred is that the dolphins are successful with getting the fish into a central location. Then they send out signals to the fishermen that inform them where they should drop their nets to catch the fish. It is very evident the social and cooperation skills of these dolphins are extremely well developed.

Additional research on these dolphins also shows they are extremely social and cooperative within the group. This is based on information that has been published in the Royal Society Biology Letters if you are interested in finding out more. It is believed that these factors help to explain why some of the dolphins in the wild do help humans and other don’t take part in it.

The behaviors are well synchronized and fishermen have been able to rely on those signals. They often include tail or head slaps in the water in given locations. The fishermen are able to quickly put their nets in the right place. This allows them to get the fish instead of guessing where to put the nets and hoping for the best. Such information has been observed and documented by Fabio Daura-Jorge of the Federal University of Santa Catarina.

Along with several colleagues, he has been able to see the outcome of such experiences. So what is in it for the dolphins? They get to dine on the fish that find their way out of the nets. They are patient and wait for that moment to arrive. Such observations were noted by Daura-Jorge and his team through boating surveys that took place over the course of a 2 year period.

They used photos to identify the dolphins. This allowed them to classify the groups as cooperative or non-cooperative based on their interactions or lack of interactions with the fishermen. The use of computer modeling allowed for the social relationships among the dolphins to be successfully identified.

What was found is that those dolphins that were cooperative spent far more time with each other, even when they weren’t participating in activities that helped the fishermen. It is believed that there are many factors at work here that determine if a relationship will occur naturally between humans and dolphins. They include genetics, social learning, and ecology. 

It is believed that information transferred from one generation of the dolphins to the next is very important here. The older dolphins teach the younger ones to be able to successfully help the fishermen. There have been numerous documentations about such behaviors within groups of dolphins in various areas. One that is widely discussed is the process of sponging by the dolphins in Shark Bay, Australia. If you aren’t familiar with sponging, it is the process of these Bottlenose Dolphins tearing pieces of sponges and covering their snout with them while they forage for food. This protects them from damages to that part of the body. 

There are plenty of unique behaviors identified within dolphin groups, and their intelligence level is believed to be a big part of them. According to Lori Marino from Emory University, the size of the dolphin’s brain should be used to help measure their intelligence. She and many others believe the dolphin ranks #2 – right being humans.

Source: http://news.discovery.com/animals/helpful-dolphins-120502.html

Bottlenose dolphins diet consists mainly of small fish with occasional squid, crabs, shrimp, and other smaller animals.

Their teeth are not used to chew the food. When they find a shoal of fish, dolphins work as a team to keep the fish close together and maximize the intake. They also search for fish alone. Sometimes dolphins employ “fish whacking” where a fish is stunned (and sometimes thrown out of the water) with the fluke to catch and eat the fish easier especially when dealing with large specimens.

In some Mediterranean areas sometimes there is a conflict between common Bottlenose Dolphins and small-scale commercial fisheries looking for the same prey. Common Bottlenose Dolphins are probably attracted to fishing nets because they make easier for dolphins eat from a concentrated food source.

There are several species of herring, being the most common the Atlantic Herring.

This species is registered as the most available fish in the ocean by the Guinness book of records, which makes them at the same time, the most hunted species by dolphins.

The Atlantic Herring dwells on both sides of the Atlantic.

Spinner dolphins eat several kinds of fish, jellyfish, squid, krill and some types of snails that lack the shell.

Although spinner dolphins gather in small groups for hunting, they remain coordinated with sounds and the usual whistles.

They usually submerge from 250 to 1,000 meters deep to hunt their prey. Eels, shrimp, and lanternfish (myctophids) also complement their diet.

Pacific white-sided dolphins inhabit the temperate waters of the Pacific Ocean from Baja California, Mexico to Alaska. Therefore it eats some of the common species of fish in these regions. Among them, herring, sardines, salmon, anchovies, squid and some other small fishes.

This dolphin consumes about 9 kg of food every day and can be organized into groups to chase and ambush fish to eat more efficiently.

The food that dolphins eat is different for each species.
While some dolphins eat fishes like herring, cod or mackerel, some others eat squids or other cephalopods.

Even more, large dolphins like killer whales, eat marine mammals like seals or sea lions and sometimes even turtles.

Usually, the amount of fish that they eat depends on the kind of fish that they hunt. While mackerels or herrings have a lot of fat, squids do not have much fat, therefore, to get the energy required for their activities, dolphins have to eat more of the latter.

On average, a dolphin with a weight of 200 – 250 Kg will eat between 10 Kg to 25 Kg of fish every day.

Usually, to hunt fish, some species of dolphins use a method called herding which is a cooperative hunting performed by a pod where some of them surround a school of fish to compress them as much as possible, while some others take turns to eat through the compacted school of fish.

Another method is corralling where dolphins take fish to shallow waters where they cannot escape.

Some species catch larger fish by hitting them with their tails to stun them and in the case of killer whales, they

Therefore the question about what do dolphins eat has to be answered for every species in particular.

In this video, you can watch a pod of dolphins working together to feed themselves and using the technique called herding to catch the fish as they surround the school of fish, and then some of them take turns to eat.

In the video, you can learn more about What do dolphins eat.

Dolphins use several methods to get their food. Fish and squid are the main sources of food for most dolphin species, and they hunt in group cooperatively to catch them.

One method called herding consist that a group of dolphins encircles a school of fish to gather them as close as possible and after that one or two take turns to swim from the bottom of the school to have the largest amount of fish possible on each pass.

It is important that they go from bottom to top because if they were from side to side, the school of fish would probably disperse.

The second method is called corralling, which is performed taking fish to shallow waters where dolphins can just capture them.

Some species are even more specialized or with unique techniques to catch fish or other particular prey that only they consume, like killer whales hunting seals, for example.

The Chilean dolphin, also known as the black dolphin is a small dolphin native to the coast of Chile and it is the only place in the world where it inhabits.

They eat small species of fish, cephalopods, and crustaceans. In a few specimens analyzed, also seaweed remains were found. Sardines, sea bass or anchovy are their preferred species of fish.