Морские котики и не только: разнообразие ушастых тюленей
Do Seals Live in the Sea? An Introduction to Pinnipeds
Overview of Pinnipeds
- The lecture begins with a discussion about pinnipeds, specifically focusing on earless seals and their characteristics.
- Pinnipeds are widespread, inhabiting all oceans globally, including freshwater environments like Lake Baikal in Russia.
Physical Characteristics
- Pinnipeds have a streamlined body shape for efficient swimming; their limbs are adapted into flippers.
- They vary significantly in size; the smallest seal weighs around 50-60 kg, while some species can be much larger.
Habitat and Behavior
- Most pinnipeds spend approximately 10 months of the year in water but must come ashore to breed.
- Differences between true seals (like the harbor seal) and eared seals (like sea lions) include external ear presence and mobility on land.
Distinctions Between True Seals and Eared Seals
Movement and Swimming Techniques
- True seals move awkwardly on land using their bodies, while eared seals can walk on all fours using their front flippers.
- Eared seals can swim faster than true seals, reaching speeds up to 30 km/h by using their front flippers for propulsion.
Diving Abilities
- Both types of pinnipeds typically dive for about 20 minutes at depths of around 300 meters; however, some species like southern elephant seals can dive over a kilometer deep.
Specific Species: Northern Fur Seal
Habitat and Social Structure
- The northern fur seal is a classic harem species where one large male dominates a territory during breeding season.
- Males establish territories on islands in the Russian Far East around late May to early June, with females arriving shortly after.
Reproductive Behavior
- Females usually give birth to one pup after mating with the territorial male. This occurs shortly after they arrive at breeding grounds.
Maternal Care and Pup Development
Nursing and Social Interaction
- After giving birth, mothers leave pups for feeding trips lasting several days. Pups initially stay put but begin socializing with others around two weeks old.
Finding Each Other
- Mothers locate their pups through vocalizations amidst large colonies. Pups recognize maternal calls as part of their bonding process.
Reproductive Behavior and Lifespan of Northern Sea Lions
Interaction and Breeding Season
- The video describes the interaction between a pup and its mother, highlighting their initial meeting where they sniff each other before feeding.
- Female sea lions are ready to mate by two years old, while males typically reach maturity at four but often do not compete until around eight years due to weight issues.
- Males face intense competition for territory; many exhaust their resources within 2-3 years, leading to a shorter lifespan of 15-17 years compared to females who can give birth until age 35.
Distribution and Conservation Status
- The northern sea lion (Steller's sea lion) is highlighted as a red-listed species in Russia, with all breeding grounds being protected areas.
- Despite protections, populations continue to decline in certain regions both within Russia and internationally.
Breeding Patterns
- Steller's sea lions arrive at breeding sites earlier than northern fur seals, with males arriving in late May followed by females shortly after.
- Unlike northern fur seals, only about 50% of females mate with the male on whose territory they give birth; others may mate with neighboring males or those waiting in the water.
Pup Development and Social Structure
- Each female typically gives birth to one pup weighing around 12-16 kg. Pups stay close to their mothers initially for care.
- A unique aspect of Steller's sea lions is that mothers leave the breeding ground together with their pups for training on hunting skills.