Echolocation; Something else of interest from my Marine Biology class

Echolocation was  another interesting study from my Marine Biology class. We all know that bats use it, and of course dolphins and whales, but did you know that even shrews use a primitive type of echolocation?                                                    

                                              Echolocation

                                              

      Echolocation as defined in Marine Biology written by Castro and Huber is the ability of some animals to sense their surroundings by analyzing the reflection of sound waves, or clicks, they emit. Another name for it is bio-sonar. Animals create sounds of different pitches, and then listen for the echo. This helps them determine the distance, and size of the object. It is usually used in place of vision. It helps with navigating in their environment, and in the locating food. It can also be used for social interaction. This is seen more in marine animals.

     Echolocation is used by several animals. It is used by Dolphins and Whales, bats, birds like Swiftlets and Oilbird’s, Shrews and Tenrecs, and at times even by humans.  People with vision impairments seem to be more likely to benefit from echolocation. When one sense is disabled the other senses become heightened which would seem to be the case with people without vision. There are classes that can be attended to learn to use this ability. Of course humans have found many uses for sonar.

     Whales and Dolphin both depend on echolocation for their survival. The sounds they make are different, but the results are similar. Whales make high pitched groans and whistles while dolphins make sounds from their nasal tissues that sound like clicks. They both use it to navigate, locate food, communicate, and avoid predators. It is a very sophisticated language.

     Whales produce sound when air passes through the phonic lips and there is a vibration. When it opens and closes it produces a clack. This causes vibrations that pass sound waves to the melon which is filled with fatty liquid and acts as an acoustic lens. From there it is directed towards the target and emitted from the front of the forehead. (Echolocation; pg3)

Diagram illustrating sound generation, propagation and reception in a toothed whale. Outgoing sounds are red and incoming ones are green

Biosonar
en.wikipedia.org/wiki/Animal_ecolocation

Sound waves travel better through water then through the air, because it requires a high density medium to be efficient. The sound is different in water in comparison to the way it sounds in the air. Water is denser then air, so it transmits more efficiently. Traveling through air it loses energy. It may sound louder under water, but it isn’t. It has retained more of its energy. This makes echolocation a very effective way for whales and dolphin to communicate.

     There are terrestrial animals that use echolocation. The Oilbird (Steatornis caripensis) is nocturnal, and rests in caves during the day. It leaves to find food at night. It forages by sight, but navigates by echolocation in poor light conditions. It uses a series of sharp audible clicks for this purpose. Swiftlets also use echolocation. They use it to locate their roost in a dark cave. Their clicking noise is well within human hearing range. The clicks consist of two broadband pulses (3-10 KHz) separated b y a slight pause (1-3 milliseconds). The interpulse periods are varied depending on the level of light

     Microbats also use echolocation. The sounds that they emit are beyond human hearing. Bats are blind, and so echolocation takes the place of their vision. They use it to navigate and forage. It is emitted through the larynx and out the mouth. There are some bats that emit the sound through their nose. They help keep the insect population down. They emit a sound at a frequency of about 14,000 to over 100,000 Hz. Different bat species echolocate within specific frequency ranges that suit their environment and prey type.

 

A depiction of the ultrasound signals emitted by a bat, and the echo from a nearby object.

en.wikipedia.org/wiki/Animal_ecolocation

     Shrews and Tenrecs use echolocation, but their sound is a low amplitude, broadband, multi-harmonic and frequency modulated. It seems to be used for close range spatial orientation. They use it to investigate their habitat as well as to search for food. They use the echoes to locate insects and other prey They open and close their mouths rapidly to emit quick pulses of low intensity sound as they get near their prey.

 The terrestrial animals that use echolocation have a more primitive version of echolocation, and use it for simpler purposes. The marine animals that use it appear to have a more sophisticated system using it not only for navigation and food searches, but for communication between individuals. 

      

                                                                        Work sited

Animals That Use Echolocation/eHow.com.  http://www.ehow.com/info_8576794_animals-use-echolocation.htlm

Animal echolocation-Wikipedia, the free encyclopedia     http://en.wikipedia.org/wiki/Animal_echolocation

Blind People’s Ability to Echolocate.  http://www.disabled-world.com/disability/types/vision/echolocate.php

Can sound travel through water.  http://wiki.answers.com/Q/Can_sound_travel_through_water

Echolocationand BioSonar/Sonography. http://www.sonargraphy.net/resources/echolocation-and-biosonar/

Microbats-Wikipedia,the free encyclopedia.  http://en.wikipedia.org/wiki/Microchiroptera

Oilbird- Wikipedia, the free encyclopedia.  http://en.wikipedia.org/wiki/oilbird

Swiftlet-Wikipedia, the free encyclopedia.  http://wikipedia.org/wiki/Swiftlet

Love Marine Biology and turtles in general and Leatherback Sea turtles especially

I took a class in Marine Biology, and I loved it. True I only got a B in the class, but I read every word in that book in the beginning the last two weeks the reading was so extensive I failed to complete it, and I rented the book instead of buying it. I had to return it. That was sad. I would have loved to keep it. Of course I am a geek. I very often keep my books. I was reading through my geography book, and someone told me they would rather sit in a room with white walls and stare than read a geography book. 

I am fascinated with turtles, so I enjoyed writing about Leatherback Sea turtles. I hope you enjoy the information.

 Leatherback Sea Turtles:

D. Coriacea is listed on Appendix 1 of CITES, which makes export/import of this species (including parts) illegal.

     The Leatherback Sea Turtle is the largest of the sea turtles. It can grow to Six and a half feet, and weigh up to 1,400 pounds. Unlike other marine turtles it has a carapace that is covered with skin and oily flesh. The Leatherback turtles have been around for 110 million years in one form or another. They began during the crustaceous period. They are a close relative to the other six species of sea turtles that still exist today.

     Leatherback mothers lay eggs, and leave them to hatch. The infant Leatherbacks face the same challenges as other sea turtles as they try to make it to the sea. It must be like running a gauntlet. There are a variety of predators ready to eat them. This is if humans have not already eaten the eggs. Once at sea they face predation from cephalopods, sharks and other large fish. They don’t have a hard shell, but as adults they face fewer predators. They can be quite aggressive if attacked at sea.

     They do long distance migrations from cold water to tropical beaches where they hatch.  They breed in water, and the males once they hatch and reach the ocean will never return to land. The females will return to lay eggs. They mate every two to three years, and fertilization is internal. Multiple males breed with a single female which doesn’t appear to provide the offspring’s with any advantages. They do not always return to the place where they were hatched, but may choose another beach in that region. They like beaches with finer sand, because their shells are soft and plastrons are easily damaged by hard rocks. They nest at night, and prefer to nest on a beach near a forest. Their night vision on land in poor. The dark forest and the moonlit ocean help the female with directions. She makes the nest above the high tide line, and digs it with her flippers. She will lay about nine clutches of eggs in a breeding season of around 110 eggs each. 85% will be viable. She covers her nests and disguises it by scattering sand. The eggs hatch in 60 to 70 days. The nests ambient temperature determines the sex of the babies.

     They live mainly in the open ocean. They can travel from Indonesia to the US which would be about 12,000 miles. Their prey is jellyfish, so they are in deeper water during the day and more shallow water at night. They are undaunted by cold water or deep water. They also feed on tunicates and cephalopods.

     One reason they are endangered is because plastic bags float and resemble jellyfish. It is estimated that a third of the Leatherbacks have ingested plastic. It obstructs their digestive tract, and inhibits their ability to get nutrients they need. This stops growth which effects sexual maturity and limits reproduction. This is the best case scenario. The worst case is that they starve to death.

      Their life span is undetermined. It is believed it is somewhere between thirty and eighty years.

     They are the largest living sea turtle and as such the turtle excluder’s devises can be ineffective with mature adults.  It was reported that 1500 mature females were caught accidentally annually in the 1990’s. Pollution like chemicals can be fatal. A high level of phthalates has been measured in their egg yolks.

Work Cited

Leigh Henry: WWF Marine Turtle Leatherback Turtle. http://worldwildlife.org/species/leather_turtle

Leatherback Sea Turtle. En.wikipedia.org/wiki/leatherback_turtle

Leatherback Sea Turtle. www.bagheera.com/inthewild/van_anim_turtle.htm

Nancy Haydon; Why is the Leatherback Sea Turtle Endangered. http://www.ehow.com/about_7229211

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