The harbor or harbour porpoise can be found swimming in locations such as the north Atlantic, north Pacific, the Black sea and west Africa.
As the name suggest these porpoises tend to swim in or around harbors in coastal waters.
Not much is known about their social structure as a group though they do prefer to travel in small pods of 4 – 5 porpoises and rarely intermingle with other marine species.
For the most part they spend their time living in a specifically isolated locations, however they have been observed traveling on and offshore along the coastline from time to time.
Physical Characteristics and Appearance
In terms of size these marine mammals can grow to lengths of just over 6 feet and weigh between 100 – 200 pounds.
While the males tend to grow to the same length as their female counterparts they typically weigh around 30 pounds less.
The back, flippers and dorsal fin are dark gray while the belly is a much lighter whitish color.
The head also appears to be more v shaped instead of having a protruding beak as seen in some species of dolphin (a suborder of the cetacean species).
Diet and Hunting Methods
These porpoises have been known to eat squid, crustaceans, fish, capelin and herring.
They generally prefer to hunt individually, but will on occasion forage as a group with other porpoises.
Most hunting occurs near or at the bottom of the water in shallow waters.
In larger deeper waters they can be observed hunting fish at mid level.
During extended hunts these marine mammals have been observed staying submerged for up to 5 minutes before resurfacing for air and making dives of up to 720 ft. deep.
Habitat and Migration
As the name suggests the harbor porpoise can be found inhibiting coastal temperate waters near bays, estuaries, harbors, rivers and tidal channels.
These marine mammals can be found swimming throughout various parts of the Northern hemisphere in the North Atlantic and North Pacific ocean as well as the Black Sea.
Harbor porpoises generally prefer shallow waters of less than 1,000 – 500 ft.
While these marine mammals aren’t really known for making long migration trips they have been observed migrating back and forth from coastal to offshore waters.
Social Structure and Communication
When it comes to the social lives of harbor porpoises little is known about them and how they live.
The harbor porpoise is a relatively passive ocean animal when it comes to communication with others.
They are generally found either traveling alone or in small groups of up to 5, however they may occasionally be spotted feeding in groups of up to 100.
They also tend to prefer staying within a certain range and generally do not leave their local habitat for very long when they travel.
When approached by boats the harbor porpoise prefers to keep its distance and may shy away from approaching aquatic vehicles.
Breeding and Reproduction
The average gestation period (the period from conception to birth) for harbor porpoises is 10 – 11 months.
After birth the female porpoise may continue to nurse her young for up to 12 months.
Harbor porpoises produce one offspring every 2 years or so while they are fertile.
It is believed that female porpoises reach maturity between the ages of 3 – 5 where they are then able to begin mating and reproducing.
Threats
In the past harbor porpoises were hunted for food and blubber which was used as an ingredient for fuel and as an additive in certain chemicals.
Because of their close living quarters with the harbors these porpoises were ideal targets for whalers.
Today however their primary threats including getting accidentally caught in fishing nets, suffering from both water and noise pollution, global warming and struggling to find food due to over hunting from fisheries.
Bycatch – One of the most common threats the harbor porpoises face today is drowning in the fishing nets that they get caught in.
While intended for fish the harbor porpoise can easily swim into a large net, become entangle and unable to swim causing it to drown due to a lack of fresh oxygen.
Pollution – Seeing as how the harbor porpoise inhibits coastal waters they may face threats from various forms of pollution including chemical waste, physical materials and even noise pollution.
In the case of noise pollution some researchers believe that loud man made sounds can interfere with echolocation and the porpoises ability to detect natural sounds.
Over-fishing – In some areas over fishing can affect a harbor porpoises ability to find sufficient amounts of food.
As more fishermen take to the water and grab up fish it makes it more difficult for the harbor porpoise to maintain its dietary needs.
In some cases this can also lead to increased competition for food resources among other competing marine mammals such as bottlenose dolphins.
Predators
The harbor porpoise is known to be hunted and attacked by numerous predators that are either looking for food or trying to limit competition for prey resources such as fish.
Natural threats include being attacked and eaten by sharks, killer whales and even grey seals.
In some cases these marine mammals are also attacked (but not eaten) by bottlenose dolphins who compete with them for food resources.