Fossil Record
• Shows that some land animals began to make the transition to sea animals about 50 million years ago.
Mammals
• Whales are mammals and all mammals share 3 characteristics:
– Hair
– Feed young with milk from mammary glands
– Have a 4-chambered heart
Baleen Whales• Two blowholes
• Baleen plates – filter feeders
Plates grow to several feet in length
May be several hundred in one animal
• Flat on outer edge, bristles on inner edge trap small organisms
• Krill: food source for many baleen whales
• Includes the humpback, blue, finback, right, sei, and gray whales.
Toothed Whales• One blowhole
• Have teeth to seize prey
• Include the Sperm, killer, pilot, beluga, dolphins and porpoises
• Killer whales: top carnivores
Whale Reproduction• Fertilization and development are internal
• Whales breed about every 3 years and the female whale, or “cow”, stays pregnant between 11 and 18 months.
• Whales are born tail first.
• Nurse for 6-10 months
• A blue whale calf drinks the equivalent of 400 glasses of milk per day and the milk is 50% fat in content.
Adaptations and Behaviors
• Whales breathe through their blowholes which are connected to their lungs, not their stomachs (Dory and Marlin would never have been shot out the blowhole).
• Blowhole is on the dorsal side of their bodies, up on their head, so it surfaces first
• Baleen whales have 2 blowholes, toothed whales have 1 blowhole
Swimming• Whales swim by the up and down
movement of their hind flippers or tail flukes
• The dorsal fin helps keep them on course
• Pectoral fins are used for steering, braking and balance.
• The bones inside the fin are similar to the bone structure of the hands of land mammals and whales still have hip bones.
Diving• Whale uses its pectoral fins to change from horizontal to vertical.
• The tail flukes then push the body down into the water head-first
Lobtailing• Waves tail in the air
then smashes it into the water.
• Not fully understood by scientists
• May be a sign of aggression or a way to announce its presence.
Spyhopping• Whale raises
head above the water’s surface to look around for a few seconds.
• May be a sign of curiosity
Whale Migration
• Whales spend the summers feeding in the waters off the Bering Sea and Arctic Ocean. These waters are nutrient rich and contain a lot of plankton.
• During the winter, whales migrate to warmer, shallow waters around Baja California (Gray Whale) or Mexico (Humpback) to breed and have their young.
Echolocation- form of sonar where the whale bounces sound off of objects to detect objects in the water
Stranding• Stranding is where a dolphin or whale swims
into shallow waters and becomes beached. • The whales die as their internal organs are
crushed by their own body weight.• It is puzzling because, for whatever reason,
their echolocation system is not working.• May be caused by PCBs and DDT or natural
toxins in the water.
Mass Stranding
Pilot Whales are the most commonly stranded whale. May have been caused by the use of sonar by navy ships.
Threats to Cetaceans• 1. Hunting – both regulated and
unregulated• 2. Pollution – PCBs and DDT may
interfere with echolocation causing strandings– Oil slicks also a big problem
• 3. Overfishing or killing of whales’ food source(s).
• 4. Noise – interfering with echolocation• 5. Unintentional tangling in nets used for
other purposes (dolphins in tuna nets)