Lesson 14: Ocean Wave and Magnitism

Question 1

Nesting Loggerhead sea turtle

Answer 1

• lays about 100 eggs
• ## buries eggs and leaves

Question 2

Hatching

Answer 2

• sense that it’s dark outside and crawl out of the sand
  – sense that its dark by the cooling of the sand
  — also happens when it rains
• turtles find the sea by crawling to the lowest, brightest horizon and away from the large, dark vegetation

Question 3

light pollution

Answer 3

some hatchlings will crawl to cars or street lights because it is the brightest thing and they crawl towards the brightest thing which is supposed to be the ocean

Question 4

2 journeys the hatchlings have to make

Answer 4

• crawl from nest to sea
• swim offshore to the Gulf Stream Current to where they ear sargassum weed

Question 5

The Gyre Migration

Answer 5

• post hatchling or pelagic juveniles spend their time in the Gyre
• as “pelagic juveniles” turtles spend approx. 10-15 years in the Atlantic ocean, their “nursery” habitat
• known as the great migration
• coastal juveniles become benthic and establish coastal feeding sites after 10-15 years in open ocean; they are able to come home back to those sites when displaced — very loyal l
• aduly turtles make regular migrations between feeding sites and breeding sites
• they are aslo known to breed in areas where they themselves had hatched:

Question 6

what is it called when turtles breed in areas where they were hatched

Answer 6

natal homing

Question 7

the offshore migration

Answer 7

use of wave cues
– when the baby turtles get in the water they instantly known where to swim
- swim in the direction of the waves
- used a digital compass to measure the vanishing bearing for each

Question 8

wave data

Answer 8

• did didn;t matter which direction the waves came from, the turtles swam into the waves

Question 9

wave terms

Answer 9

• beach
• final wave direction
• wave refraction zone
• open ocean
• initial wave direction

Question 10

sensing waves

Answer 10

• turtles cannot sea the waves
• they sense them from below the surface
• if facing forwards and a wave comes from below, they move up, back, down, and then forwards

Question 11

turning

Answer 11

left turning - left flipper out
right turning - right flipper out

Question 12

experiment - turtles an waves

Answer 12

can position the turtle so that the artificial waves come from different directions: here the turtle faces it of the screen so that “waves” would seem to come from its right

Question 13

with a magnetic coil system, the magnetic field around a swimming turtle can be changed

Answer 13

north is south
— switch directions

geometric horizontal field - coil field = resultant field

Question 14

experiment: compass

Answer 14

attached turtle to a rotating arm

In tank in normal field, swimming to light in east
- light off –> exposed to NORMAL magnetic field of the earth –> or exposed to the a REVERSED field where north feels like south

Results: Loggerhead hatchlings
1.) can detect magnetic fields
2.) use earth’s magnetic field as a compass for telling one direction from another

Question 15

choice of direction in the orientation area

Answer 15

• if a turtle swims towards an east light and is then tested in darkness, then it will swim east
• if a turtle swims towards a west light and is then tested in the darkness, it will swim west

Question 16

in the real world

Answer 16

• turtles pay attention to light while crawling on the beach
• perhaps turtles in nature use light to set their magnetic compasses for the correct course towards the open sea

Question 17

artificial beach crawl

Answer 17

• there is light at the end of the runway
• just before the turtle reaches the light it is carried in complete darkness and tethered to the swimming arena to see what direction it will swim
• trials were east craw, west crawl, and east crawl (no light)

results:

• east crawl - on average east - northeast
• west crawl - average west
• no light – no preference

CONCLUSION
- they at. least have the ability to set their compass for a preference that is towards the light
- LEARNED

Question 18

hatchling turtles set their magnetic compass using environmental cues

Answer 18

can use:

1.) light cues while swimming
2.). light cues while crawling
3.) even wave cues while swimming