ABOUT TRUE SEALS

 

The earless seals, phocids, or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae (/ˈfoʊsɪdiː/). They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae. Seals live in the oceans of both hemispheres and, with the exception of the more tropical monk seals, are mostly confined to polar, sub polar, and temperate climates. The Baikal seal is the only species of exclusively freshwater seal.

AVERAGE LIFE SPAN: 25-30 years

WEIGHTS OF AVERAGE TRUE SEALS: A Male True seals weights on average about 600kg (1320lb) and is about 3.5 m (11.5ft) long, while the female True seals weighs 250kg (550lb) and is 2.5 m (8.2ft) long.

LARGEST AND SMALLEST TRUE SEALS: The largest True seal is NORTHERN AND SOUTHERN ELEPHANT SEALS which can weighs 3530kg (7780lb) for males and up to 900kg (1300lb) For Females grow to a length of 6.5m (21ft) for male and female to a length of 3.5m (11ft). The smallest True Seal is Ringed Seal which can weighs 70kg (150lb) with an average length of 1.5m (5ft).

CONSUPTION OF FOOD: Their diet typically includes fish, squid, crustaceans and cephalopods. It can dive up to 600m (1970 ft.) in search of food.

SPEED OF TRUE SEAL: They typically swim around 6mph, but can reach speeds of up to 18 mph.

GESTATION PERIOD: 8 to 15 months.

COMMUNICATION: Unlike otariids, true seals do not communicate by 'barking'. Instead, they communicate by slapping the water and grunting.

ENDANGERED SPECIES: Harp Seal, Hawaiian Monk Seal, Bearded Seal, and Caspian Seal.

SENSES OF TRUE SEAL

Earless seals, also known as true seals or Phocids, have a number of senses, including:

Hearing: They can hear in both air and water, and are more sensitive to underwater sounds. 

Vision: They have large, round eyes that allow them to focus on both air and water. 

Smell: They have a keen sense of smell in the air, which helps them detect predators. 

Touch: They have well-developed whiskers that help them feel vibrations from swimming prey. 

Blubber: They have a thick layer of blubber that insulates most of their body, except for their flippers and head. 

Seals are also known as pinnipeds, along with sea lions and walruses. They are opportunistic feeders that eat whatever prey is available.

SLEEPING POSITION OF TRUE SEAL

Earless seals, like most mammals, sleep bihemispherically, and can sleep in a variety of positions, including:

Underwater: Seals can sleep underwater while holding their breath, floating in a standing position, or floating horizontally on the surface. They regularly wake up to surface and breathe.

On the surface: Seals can hang with their nostrils above water and have REM sleep in this position.

On land: Seals can sleep on land.

Prone position: Seals can sleep in a prone (ventral) position in water.

Sleep spiral: During deep dives, seals can transition into rapid-eye-movement (REM) sleep, which causes them to lose postural control and turn upside down. They then drift downwards in a “sleep spiral”.

On the seafloor: In shallower waters, seals can sleep motionless on the ocean floor.

DIVING ADAPTATION OF TRUE SEAL

Earless seals are better adapted to an aquatic environment. Along with no outer ear flap, they have streamlined bodies, internal testicles, and a smooth layer of blubber under their skin. They can also reroute blood flow to the blubber to better control their body temperature. Earless seals, also known as phocids, have many adaptations that allow them to dive to great depths and stay underwater for long periods of time: 

Respiratory system: Seals force air from their lungs into their upper respiratory passages during a dive, which helps prevent decompression sickness, oxygen toxicity, and nitrogen narcosis. 

Circulatory system: Seals have large amounts of hemoglobin and myoglobin in their blood and muscles, which allows them to stay submerged for long periods of time. They also have an elastic aorta that helps keep their blood pressure stable. 

Blubber: Seals have a thick layer of fat called blubber that insulates them and reduces drag. Blubber is more effective than hair at insulating seals in water because it doesn't collapse under pressure. 

Streamlined bodies: Seals have sleek, streamlined bodies with no external ears, reduced limbs, and internal testicles and mammary glands. 

Blood flow: Seals can divert blood flow to their blubber to help control their temperature. During diving, they reduce their heart rate and restrict blood flow to their heart, brain, and lungs. 

Middle ear: The middle ear of seals is lined with blood sinuses that inflate during diving to help maintain constant pressure.

BREEDING METHODS AND HABITS OF TRUE SEAL

Females will give birth on shore, on ice floes and in the water. Mating resumes shortly after the female has given birth and delayed implantation appears to ensure that pups are born in the proper season with a higher survival rate. Here are some breeding methods of seals:

Habitat: Earless seals are found in various regions around the world, including the Arctic, Antarctic, and sub-Arctic regions, as well as along the coasts of the North and South Atlantic and Pacific Oceans. They can be found in areas with pack ice, rocky shorelines, sandy beaches, and estuaries.

Mating: Seals have a variety of mating strategies, ranging from monogamy to polygyny. During mating season, males compete with each other to attract females. They may not eat during this time so they don't lose a female to another seal. 

Gestation: Seals have an embryonic diapause, which means the fertilized egg doesn't immediately implant in the uterus. This can delay gestation for 8 to 15 months. 

Birth: Seals give birth on land or ice. They typically have one pup at a time, though twins can occur. 

Lactation: Lactation differs between seal families. Phocid seals, like earless seals, have an intense period of maternal investment where the mother fasts. 

Pup rearing: Mothers feed their pups for up to a month until they are strong enough to swim and live independently. During this time, mothers don't eat and rely on their blubber stores for sustenance.

GEOGRAPHIC VARIATION

Phocids are found throughout all of the world's major oceans except for the Indian Ocean. Twelve species breed on ice, six species breed on land, including the West Indies monk seal, which is probably extinct. The gray seal breeds on both land and on ice. The harp seal is a species of earless seal that lives in the cold waters of the North Atlantic and Arctic Oceans. There are three recognized populations of harp seals, based on geographic distribution, as well as morphological, genetic, and behavioral differences. Geographic variation can be seen in earless seals, also known as true seals or phocids, in a number of ways, including:

Distribution: Earless seals are found in the oceans of both hemispheres, but are mostly found in polar, sub polar, and temperate climates. The exception is the monk seals, which are more tropical. 

Sub-families: Earless seals are divided into two sub-families: the Monachinae and the Phocinae. The Monachinae includes the southern phocids, the southern and northern elephant seals, and the monk seals. The Phocinae includes the bearded seal and the hooded seal. 

Breeding: Some species of earless seals breed on ice, while others breed on land. The gray seal breeds on both land and ice. 

Vocalizations: Vocal characteristics can vary between and within populations of earless seals. Individuals may be able to distinguish between calls from local and non-local individuals. 

CONSERVATION

Since the early 20th century, they have been protected by law in both Mexico and in the United States. Subsequently, the U.S. protection was strengthened after passage of the Marine Mammal Protection Act of 1972, and numbers have now recovered to over 100,000. Human greed has led to the decline of many seal populations. In the past, millions of seals were killed for their valuable meat, blubber, and pelts. In some countries seals are still killed in large numbers because fishermen blame them for the decline in fish. Vessels can injure, kill, or disturb harp seals. The most effective way to reduce vessel disturbance is for vessels to stay away to keep seals and vessels apart. In New England, we have issued “Share the Shore” seal watching guidelines to reduce the disturbance of harp seals. Harp seals are at risk of harm in the event of an oil spill. To minimize the effect of a potential spill on harp seals, NOAA developed the Marine Mammal Oil Spill Response Guidelines. NOAA Fisheries aims to increase public awareness and support for harp seal conservation through education, outreach, and public participation. We share information with the public about the status of harp seals, as well as our research and efforts to promote their recovery.

HUMAN INTERACTION

Seals are generally gentle unless they feel threatened. Seals are wild animals that are usually solitary, but they can sometimes interact with humans. If you encounter a seal, you can try to: Let the seal make the first move, Sit back and wait quietly, and Stay calm and move slowly. Humans can negatively impact seals in many ways, including: 

Entanglement: Seals can become entangled in materials from fishing industries, especially young seals. 

Micro plastics: Seals can accumulate micro plastics through bioaccumulation, which is when a predator eats prey that contains micro plastics. 

Illegal feeding: Feeding harbor seals illegally can lead to aggression, habituation, injury, death, and negative impacts to fisheries. 

Harassment: Harassment, such as repeated exposure to vessel traffic, can degrade important areas for seals. 

Disturbance: Human activities can disturb seals, causing them to flush into the water and reducing the time they spend on land. 

Some True Seals Species In their Adult And Juvenile Forms