Structure and Functions of Organs: How Organisms are Adapted to survive in Specific Environments

Hawaii is the 50th and most recent state to enter the United States, having gained statehood in August 1959. It is also the only state that is not centered in North America, encompassing almost the whole volcanic Hawaiian archipelago, which consists of hundreds of islands scattered over 1,500 miles. Niihau, Kauai, Molokai, Lanai, Kahoolawe, Maui, and the biggest, Hawai'i, are the major islands. A variety of species are supported by the warm tropical atmosphere, varied natural landscape, oceanic surroundings, and active volcanic activity. This report discusses the Hawaiian monk seal, a mammal that thrives and has been in the archipelago for close to 14 million years.

The Environment

Located 1, 469 miles above the equator, Hawaii enjoys a predominantly tropical climate with an almost nonexistent winter. The Hawaii weather is exceptionally consistent, characterized by only minimal temperature changes in a year. For the most part of the area, there are only two seasons being summer that comes between May and October, and warm winters between the months of October and April. However, the most outstanding elements include mild temperatures through the year, moderately humid conditions, persistent north east trade winds, and significantly varying levels of rainfall within short distances accompanied by infrequent severe storms. On average, the summer daytime temperatures at sea level are 29.4 C (850 F), while winter temperatures reach a maximum of 25.6 C (780 F). At night, temperatures are roughly 100 F lesser than the day temperatures. The islands depict an assortment of different micro-environments, with each having its unique weather patterns, flora, and fauna. Due to the shielding effect of volcanic mountains and the variances in weather at various altitudes, one may find tropical rain forests, arid deserts, sunny beaches, and cool alpine areas within a span of a few miles (Noaa.gov).

In addition to supplying moisture to the air and acting as a giant thermostat to the islands, the surrounding ocean also acts as home to the numerous plants and animals that thrive in Hawaii, including the Hawaiian monk seal (Kittinger, 2014).

The Hawaiian Monk Seal

Scientifically known as 'Monachus schauinslandi', the Hawaiian monk seal is an earless seal species prevalent in the Hawaii islands. They belong to the ‘Phocidae’ or ‘true seals’ family that also includes the Mediterranean seal and the extinct monk seal.

Fig. 1. Hawaiian Monk Seal Scientific Classification

Kingdom

Animalia

Phylum

Chordata (vertebrates)

Class

Mammalia

Order

Pinniped (Carnivora)

Family

Phocidae

Genus

Monachus

Scientific Name

The mammal is characterized by a relatively small head with dark large eyes and eight pairs of cetacean teeth. Their nostrils are found at the tip of their short snouts with whiskers on each side of the snout. They do not have external ears and they are naturally known to have a white belly and a grey coat. Due to their unique lineage of evolution and convergent nature, they are constantly considered to be ‘living fossil.’ (Notarbartolo & Kotomatas, 2016)

Fig.2. Hawaiian Monk Seal (Animalspot.net)

Fig. 3. Table showing 34 pinniped closely associated with the Hawaiian monk seal (Higdon et.al. 2007)

Pinnipedia

Odobenidae

Walruses

Odobenus rosmarus

Walrus

Otariidae

Sea lions and fur seals

Callorhinae

Callorhinus ursinus

Northern Fur Seal

Arctocephalinae/Otariinae

Arctocephalus townsendi

Guadalupe Fur Seal

Arctocephalus philippii

Juan Fernandez Fur Seal

Arctocephalus galapagoensis

Galapagos Fur Seal

Arctocephalus australis

South American Fur Seal

Arctocephalus tropicalis

Subantarctic Fur Seal

Arctocephalus gazella

Antarctic Fur Seal

Arctocephalus forsteri

New Zealand Fur Seal

Arctocephalus pusillus

South African Fur Seal

Zalophus californianus

California Sea Lion

Phocarctos hookeri

Hooker's Sea Lion

Neophoca cinerea

Australian Sea Lion

Otaria byronia

Southern Sea Lion

Eumetopias jubatus

Northern Sea Lion

Phocidae

True seals

Monachinae

"Southern" true seals

Monachini   

Monk seals

Monachus schauinslandi

Hawaiian Monk Seal

Monachus tropicalis†

Caribbean Monk Seal

Monachus monachus

Mediterranean Monk Seal

Miroungini   

Elephant seals

Mirounga angustirostris

Northern Elephant Seal

Mirounga leonina

Southern Elephant Seal

Lobodontini   

Antarctic seals

Lobodon carcinophagus

Crabeater Seal

Leptonychotes weddellii

Weddell Seal

Hydrurga leptonyx

Leopard Seal

Ommatophoca rossii

Ross Seal

Phocinae

Northern true seals

Erignathini   

Erignathus barbatus

Bearded Seal

Cystophorini   

Cystophora cristata

Hooded Seal

Phocini

Histriophocina   

Histriophoca fasciata

Ribbon Seal

Pagophilus groenlandicus

Harp Seal

Phocina   

Phoca largha

Largha Seal

Phoca vitulina

Harbor Seal

Pusa hispida

Ringed Seal

Pusa sibirica

Baikal Seal

Pusa caspica

Caspian Seal

Halichoerus grypus

Grey Seal

Adaptations

Named after H.H. Schauinslandi, the German scientist who first discovered a skull in the 1899 on the Laysan Island, the Hawaiian monk seals are believed to have been in the islands for nearly 14 million years to date. Within this period, the species has been able to adapt to long-standing geographical changes in the archipelago. The typical habitats of these sea mammals include the shallow water reefs for the pupping and weaning periods, sandy beaches for hauling out, and the deeper reefs for foraging. Monk seals are top predators in the coral reefs environment. However, they exhibit extreme vulnerability and sensitivity when faced with human activities that tend to interfere with their natural habitats which may eventually lead to local extirpation and extinction. The monk seal’s slender physique has a grey coat, and white abdomen that not only distinguishes them from the harbor seal, their cousin, but also makes it easy for them to hunt their prey comprising of octopus, lobster, fish, and squid in the deep water coral beds. When not hunting and feeding, the monk seal will be found basking on the sandy beaches and volcanic rocks in their habitats. The animal’s nostrils, which are small vertical slits, are adapted for diving such that they close when the seal is under water. In addition, the slender, torpedo shaped body and hind flippers allow for agility in swimming. The streamlined bodies make them agile swimmers due to the aerodynamic body shapes. They adapted to the need for this agility by growing flipper like front and back limbs for pushing them along the water. This enables them to easily forage for food in the sea (McClenachan & Cooper, 2008).

Similar to the elephant seals, monk seals shed their hair and the outer layer of skin in a catastrophic molt that happens once every year. The most active phase of the mold takes roughly ten days during which the monk seals remain on the beach. Their hair, usually dark gray on the dorsal side with a lighter shade of silver ventrally gradually changes its color upon exposure to changing atmospheric conditions throughout the year. The seawater and sunlight turn the dark gray into brown and the silver into brown-yellow, while prolonged stay in the water gives the seals a green tinge as a result of algae growing on the skin. Hawaiian monk seals have to deal with these extreme warm temperatures in the islands and they use the temperatures of the ocean water to keep them cold. The fats they preserve in their bodies help them to survive in the much colder waters. Also, the thick layers of blubber provide superb buoyancy to the body for purposes of swimming better with added vigor and energy. Recent scientific research has identified the internalization of reproductive and sensory organs to keep them from harm while dragging as a crucial feature of adaptation (Kittinger, 2014). .

Hawaiian monk seals have the ability to reduce their heartbeat rates to as low as 4-14 beats per every 60 seconds, against a normal rate of 50-120 beats per minute. This phenomenon is useful in the conservation of oxygen, a process known as Bradycardia (Notarbartolo & Kotomatas, 2016).

Their Importance to the Ecosystem

The bigger monk seal population lives in the remote and largely uninhabited Northwestern Hawaiian Islands, with a smaller number growing in the Main Hawaiian Islands. Those in the MHI experience more human interference with some ocean users viewing the species as a threat or nuisance to conventional activities including fishing. As a result, conservation of the monk seal is not universally supported by the surrounding communities, with intentionally killed animals by shooting and other foul means being discovered over time (Kittinger, 2014).

As stated, monk seals are big predators feeding on the assortment of fishes and invertebrates in the sea. They serve the purpose of controlling the levels of numerous populations of prey in order to maintain a healthy and functional ecosystem. The extinction of these sea mammals would cause immensely significant changes in the coral reef ecosystems. In addition to the past and continuing disappearances of numerous species would eventually lead to a broken and diminished ecosystem (McClenachan & Cooper, 2008).

Would Monk Seals Survive in a Completely Different Environment?

This question would be best approached based on the diet, the living environment, and breeding mechanisms surrounding the monk seals. The Hawaiian monk seals are said to be generalist feeders who feed on a variety of foods depending on availability. Squid, eels, octopus, crustaceans, and various types of fishes form the basis of the mammals’ diet. Despite the fact that this is largely dictated by the sex, location, and age of individual seals, they are primarily known to forage in deep waters of 60-300 feet. Some go as deep as 1, 000 feet where they prey on benthic organisms. Placed in a different environment, they would probably starve to death for lack of food. Their weight, which could go up to 400-600 pounds for females and 300-400 pounds for males, would also be a hindrance to search for food on land since they would not be in a position to walk around (Kittinger, 2014).

Conclusion

One cannot tell the story of the Hawaiian Islands without speaking about the Hawaiian monk seal. This is because they are an integral part of the ecosystem. However, the Hawaiian monk seal is listed as one of the critically endangered species by the Endangered Species Act. It is therefore critical for stakeholders to take necessary steps in preventing the decline of this phenomenal creature. Acquiring superior knowledge of their lifestyle and how they are impacted by the changing environment is the best way of protecting them. The comprehensive and scientific methods applied should control the thriving human activities which have served to create havoc for many living organisms in the world.

References

Climate of Hawaii. Retrieved on 31st July 2017 from http://www.prh.noaa.gov/hnl/pages/climate_summary.php

Kittinger, J.N. et.al. (2014). Historical and Contemporary Significance of the Endangered Hawaiian Monk Seal in Native Hawaiian Culture. Protected Species Division (PSD), Pacific Islands Regional Office (PIRO) of the National Oceanic and Atmospheric Administration’s (NOAA) National Marine Fisheries Service.

McClenachan, L. & Cooper, A. (2008). Extinction rate, historical population structure and ecological role of the Caribbean monk seal. Proceedings of the Royal Society B. 275: 1351-1358.

Higdon, et.al. (2007). Phylogeny and divergence of the pinnipeds (Carnivora: Mammalia) assessed using a multigene dataset. BMC Evolutionary Biology. 7 (216);

Notarbartolo, S.C. & Kotomatas, S. (2016). Are Mediterranean Monk Seals, Monachus monachus, Being Left to Save Themselves from Extinction? Advanced Marine Biology. 75; 359-386