Stellar's Sea Cow

Kingdom Animalia

Phylum Chordata

Subphylum Vertebrata

Class Mammalia

Order Sirenia

Family Dugongidae

Genus Hydrodamalis

Species gigas

Stellar's Sea Cow was more closely related to dugongs than manatees, though it was a separate genus from the modern day Dugong itself. It lived in the Bering sea, stretching from Alaska to Kamchatka. They could reach lengths of over 30 feet, and weighed up to 8,800 pounds! It is believed they grew this large to avoid the ill effects of the cold waters in the north, and to protect against predators.

The Stellar's Sea Cow was algivorous, feeding mainly off of kelp. It had no known natural predators. But humans were the major predator of the Stellar's Sea Cow, from 1741-1768, and hunted them to extiction.

Stellar's Sea Cows were described as monogamous, and as being quite protectiive of their young.

Stellar's Sea Cows were bouyant, and could not dive, unlike their dugong cousins.

Stellar's Sea Cows fasted during winter, due to the lack of kelp.

In Sea Cow specimens, no "hands" are found. Some believe that this means the Stellar's Sea Cow gradually lost its hand bones over time.

While most modern sirenians are grey in color, Stellar's Sea Cow was a dark brown, with the occasional white splothces.

Stellar's Sea Cows had no teeth but instead had bony plates for grinding kelp.

Georg Wilhelm Steller discovered Hydrodamalis gigas in 1741. The native peoples of the area had already reduced their population to a very small number, about 2-3,000. Russian whalers on their way to Alaska hunted the Stellar's Sea Cow for its meat and its blubber. By 1768, a mere 27 years after its discovery, the last of the Stellar's Sea Cows died out.

The Stellar's Sea Cow was a fascinating creature, having survived the Holocene epoch, the last ice age, and native hunters until finally being slain by europeans in the eighteenth century. It serves as a reminder of how delicate many of are ocean's creatures really are, and as a warning of what could happen to the remaining sirenians in the future, if we do not protect them. They are all endangered.

Morphed -- When Whales Had Legs -- National Geographic Cetacean Evolution

1. What helped Phillip Gingerich decide what kind of fossil he had found?

Gingerich discovered a Sygmoid Process, a part of the structure of the inner ear, that is unique to whales.

2. Why does Pakicetus go into the water in the first place?

The climate changed to arid conditions, and as the planet warmed, marine life flourished, while many of the common prey items of Pakicetus on land went away.

3. What was the problem in the water for Pakicetus?

One of the main problems facing Pakicetus was predation. Pakicetus was still far away from being an efficient, streamlined swimmer like modern whales. It most likely had to paddle like a dog, making it an easy target for Crocodilians.

4. According to Hans Thewissen, how has Pakicetus adapted to life in the water?

Tail develops muscles and flattens like that of an otter. Back legs shorten and widen to act like flippers. The body becomes more streamlined.

5. Thewissen named the new species Ambulocetus natans, which means-------?

Ambulocetus natans means "The walking and swimming whale."

6. How do they know if it lived in the sea full time?

In order to tell wether Ambulocetus lived permanantly in the oceans, you have to determine if it could have drunk seawater. A land animal wouldn't be able to handle the extra salt, while a marine animal could.

7. It really drank...?

Ambulocetus natans drank freshwater.

8. Ambulocetus vanishes from the -------------- 49 million years ago

49 million years ago, Ambulocetus vanishes from the fossil record.

9. How has the new species adapted to living in water?

A shorter, more powerful neck for better diving; rear legs widen and become more flipper-like; tail develops muscles.

10. The key to Rotocetus success in the ocean is linked to its organ of balance in the inner ear. It is much smaller in whales, allowing it to be acrobatic and agile enough to avoid predators.

11. Basliosaurus lived in the shallow Tethys sea 39 million years ago. What does Basilosaurus mean?

Basilosaurus means "King lizard." (When first described, scientists thought it was a Mosasaur.)

12. What adaptations does Basilosaurus have?

Exceptional eyesight; Improved underwater hearing; long thin body shape to hunt in shallow water.

13. Even though Durodon is much smaller than Basilosaurus, what may have helped it survive?

It is believed that Durodon might have travelled in pods.

14. 36 million years ago, ----------------- died out. why?

Basilosaurus died out 36 million years ago. The climate was cooling, causing sea levels to drop. Basilosaurus was adapted to hunting in shallow waters, and due to the loss of its habitat, it had to try and dive, which it was not designed to do.

15. ------------------- is the whale that gives rise to modern whales.

Durodon survived to become the lineage that would give rise to today's whales.

16. 30 million years ago Megalodon ate Durodons. What did Durodons do that helped them survive?

Durodon migrated northwards over time, to escape Megalodon.

17. How have modern whales adapted to deep diving?

Modern whales can control the flow of blood to their hearts and brains.

18. Today, there are more than 80 whale species.

19. The Grey Whale can swim more than 12,000 miles in an annual migration.

20. Orcas can reach speeds of 34 miles per hour.

21. Bowhead whales can live for over 200 years.

Analyzing a Scientific Article and a Project on Bird Beaks

The first part of my assignment was to read a scientific article and answer some questions about it:

1. What 3 reactions do shorebirds usually have to the presence of humans?

a. Watching the humans

b. Walking away from approaching humans

c. Flying over to an undisturbed section of beach

2. What is the potential consequence of these reactions?

Abandonment of the sections of beach with humans, including foraging areas

3. What does foraging mean?

Foraging is searching for food.

4. How many beaches were studied and where were they located (general area)?

13 beaches in Ventura County, CA

5. How often was data collected? What affected the number of days between surveys?

a. once per month

b. Tides

6. What 3 things were counted during surveys?

a. Shorebirds

b. People

c. Dogs

7. Over what period of time did the entire study take place?

June 1994-May 1997

8. What were the total counts of birds, humans, and dogs during this time?

Birds: 22,087, from 23 different species

Humans: 3,629

Dogs: 528

9. Define the following:

Mean: the average, derived by adding up all the numbers and then dividing by the number of terms

Standard Deviation (SD): a number that indicates the variance between two values

Range: the difference between the lowest and highest values of a data set

10. What assumption did the researchers make about the relationship between shorebird abundance and the presence of humans/dogs?

That the number of shorebirds would be directly affected by the number of humans and dogs.

11. Was this assumption correct? Why or why not?

It was not correct. There are other factors that could affect the result, including the physical characteristics and conditions of the habitat and the availability of prey.

12. What were some reasons other than human/dog use that might affect the number of shorebirds on a particular beach?

Physical characteristics of the habitat, such as the slope of the beach and the height of the waves, as well as the availability of prey.

13. Which beach had the largest mean number of shorebirds? Of humans? Of dogs? Which had the least for each? Looking at the entire data set for Table 1, does there appear to be a correlation between the abundance of shorebirds, humans, and/or dogs? Explain your answer.

Ormond 1 has the largest mean number of shorebirds; Marina beach has the largesr number of humans, and Silver Strand has the most dogs. Hobson beach had the fewest birds; Deer Creek had the least amount of people, and Ormond 2 and 3 had the fewest dogs. There do seem to be fewer shorebirds at beaches with lots of humans.

From the fact that there were more shorebirds on beaches with few people, I would infer that there is a correlation of some sort. However, there is a lot of variation in the data, and there could be more than one reason for the correlation. Correlation isn't causation.

14. Looking at the data for the 3 Ormond Beach sites, what did the researchers think about the possible relationship between shorebird abundance and human presence?

The researchers concluded that the population of birds at the Ormond Beach sites was due to a consistently low human population.

15. Did the researchers find that the number of shorebirds was impacted by the presence of humans/dogs? Was this the result they expected when they started this study?

The researchers came to the conclusion that the presence of humans affected the shorebird population, while the number of dogs had little effect, which surprised the researchers due to the dogs being frequently observed chasing the shorebirds.

16. What problems with their approach do the researchers admit to?

Counts were conducted only once a month, from Monday through Friday. Meaning that there was no accounting for weekend fluctuations, or for an increase in people on holidays.

17. What would you have done differently to create a more scientifically accurate study?

I would conduct counts once per week, and alternate between counting on weekdays and weekends. Also counts should be conducted at the same time of day, to avoid inconsistencies.

The second part of my assignment was to do a project showing the difference is the beaks of birds with different feeding strategies.

Surface skimmers fly right above the surface of the water and stick their elongated lower jaw under the surface of the water, snapping up any fish unlucky enough to be in their path.

Examples: Black skimmer (Rynchops niger); African skimmer (Rynchops flavirostris.)

A scything beak is used by wading birds to pick small prey items out of the mudflats.

Examples: Pied Avocet (Recurvirostra avosetta) American Avocets (Recurvirostra americana.)

Aerial fishers have a sharp, spear like beak, perfect for quickly striking and stabbing their prey.

Examples: Pied Kingfisher (Ceryle rudis) Great Blue Heron (Ardea herodias.)

A pursuit fisher actively chases after its prey, instead of ambushing it. The bill is wider than an aerial fisher's, and often has a hook at the end for grabbing slippery fish.

Examples: Great Cormorant (Phalacrocorax carbo); Flightless Cormorant (Phalacrocorax harrisi.)

Pelicans are famous for dip netting. Dip netters swallow a large gulp of water, then drain off the water, leaving behind fish, small crustaceans, and other such food items.

Examples: Brown Pelican (Pelecanus occidentalis); American white pelican (Pelecanus erythrorhynchos.)

Marine Reptiles Across the Ages

Around 312 million years ago ("MYA"), Amniotes developed adaptations that would keep them alive on land at all stages of their life cycle, allowing them to colonize the interior of the continents, and diversify into many groups, including reptiles. Chief among these was the amniotic egg, which had internal membranes to keep the embryo moist on dry land and allow for gas exchange from the air rather than the water. One would assume that reptiles had left the sea for good. But this is not the case. Below, I will discuss five different species of marine reptiles, each with different adapttions for life in the sea.

Nothosaurus lived in the Triassic period, about 240 MYA, and was small compared to some of the later marine reptiles, about the size of a seal. It still had a very reptilian body plan, but there were some key differences. Its feet were webbed, its tail was muscular, for swimming, and it had pointy, thin teeth designed for holding on to slippery prey. It is believed to be only semi-aquatic. Although not as impressive as some of the later marine reptiles, it is important, because something like Nothosaurus was the ancestor of the mighty plesiosaurs.

Metriorhynchus lived in the late Jurassic period, about 167 MYA. It was a crocodyliform, and had salt glands for excreting excess salt, flippers, and a finned tail. It is known to have scavenenged Leedsichthys, a massive fish, and was probably also a predator. It had long, slightly curved, conical teeth.

Elasmosaurus lived about 80 MYA, during the late Cretaceous period. It was fully aquatic, and had flippers, a short tail, a small head, and of course its defining feature: a neck longer than its body and tail combined. It probably hunted schools of fish. They were probably viviparous, i.e., had live birth. (There are fossils of other species of plesiosaur with fetuses.)

Tylosauruss was an apex predator. It had multiple rows of teeth, a long tail with a fin at the end, paddle like flippers, and scales (most marine reptile skin impressions that we have are smooth). Tylosaurus was a squamate, related to snakes and lizards, though the scientific community is still debating whether it is more closely related to snakes (because of adaptations like its extensible jaw), or lizards. It lived in the late Cretaceous, about 80 MYA.

Archelon was a magnificent chelonian, reaching up to 12 feet in length. It had many of the adaptations of modern sea turtles, including large flippers for swimming, a leathery carapace instead of a hard shell, and a robust beak for crushing shells. It likely ate mollusks and crustaceans. It lived in the late Cretaceous, about 70 MYA.