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Food Chains, Food Webs and
Human Interaction
in the
Cayman Islandsby
Courtney Stafford
“When we try to pick out anything by itself,
we find it hitched to everything else in the Universe."
John Muir, naturalist, explorer, and writer (1838-1914)
Paraphrased:
When one tugs at a single thing in nature,
he finds it attached to the rest of the world.
What is the difference between a food web and a food chain?
• A food chain only follows just one path as animals find food.
• For example:
Flower Nectar Butterfly Lizard
Plants Insects Frogs
Leaves Caterpillars Birds
Monarch caterpillar (primary consumer) eating Red Top (producer)
Paper Wasp (secondary consumer) eating caterpillar (primary consumer)
Producers• Producer –
usually a green plant that makes it’s
own food by photosynthesis.• Photosynthesis is the process by which green
plants make food in their leaves. During photosynthesis, water
and carbon dioxide
are
converted into glucose
(a sugar) and oxygen. Glucose is the plant’s food. Plants do not need all the oxygen gas that they make during photosynthesis and some of it goes back into the air. Photosynthesis is powered by energy from the sun. CHLOROPHYLL, the green substance in the plant’s leaves, absorbs energy from sunlight and converts it into a form of chemical energy that can be used during photosynthesis.
Primary Consumers
• Primary consumers – animals that consume plant matter. They are Herbivores.
• For example: snails
Primary Consumers ‐
Herbivores
• Aphids are insects that eat the sap of leaves.
Primary Consumer ‐
Herbivore• Bee eating
flower nectar. • Bees also eat
pollen. They are pollinators. When they visit flowers, they transfer pollen from one flower to another.
Pollinators make flowers produce fruit. Bees make honey from nectar.
Primary Consumers ‐
Herbivores
• A caterpillar turns into a pupa and then into an adult butterfly. Butterflies eat flower nectar.
Secondary Consumers• Secondary
consumers – animals that eat
herbivores (primary
consumers).• This assassin bug
has just killed a bee.
Secondary Consumer
• Secondary consumers are
carnivores.
• A
carnivore is an animal that eats other animals.
• Dragonflies eat other insects.
Secondary Consumers
• Frogs are carnivores, they mainly eat insects, spiders, and also slugs, snails and worms.
Tertiary Consumers
• Tertiary consumers –
animals that eat secondary consumers. They are carnivores that feed on other carnivores.
This Cayman Racer Snake eats frogs and lizards.
Omnivores• Eat both plants and animals
• Hickatees
are omnivores. They live in fresh or brackish water,
including ponds and mangrove swamps. They eat aquatic
vegetation, insects and baby water birds
Detritivores• Also known as detritus feeders, consume detritus
(decomposing organic matter). Examples are millipedes, woodlice, and termites.
Scavengers
• A carnivore or omnivore that eats dead animals.
• Solider Crabs eat fruits, seeds, vegetables, meat and dead insects.
Saprotrophs
• Are organisms that absorb soluble organic nutrients from inanimate sources.
• For example, from dead plant or animal matter, from dung etc.
Nitrogen Cycle• Horses and cows are herbivores, they eat grass and some
other plants. Plant protein is converted into animal protein.
Their dung goes into the earth and the ammonia in it
becomes part of the nitrogen cycle. Plants cannot take
nitrogen directly from the air. It has to be converted from
nitrites to nitrates, which fertilize plants.
Guano• Is the droppings of sea‐birds and bats. Guano is used as
fertilizer. Bats are Cayman’s only native mammals, there are
ten different bat species here. Some eat insects, such as
mosquitoes and some eat fruits. Cayman Phosphate
companies used to export guano for fertilizer.
Mangroves• Cayman has Red, Black, White Mangroves and Buttonwood. They have
different ways of coping with salt.
• Red Mangroves grow closest to the sea and can be easily recognized by their
prop roots. They are a nursery and a safe haven for juvenile marine animals
such as: lobsters, angel fish and snappers.
• White mangroves usually grow furthest away from the salty water and do not
have prop roots. These trees have small, rounded leaves and are closely
related to the buttonwood.
• The black mangrove can be easily identified by its numerous breathing tubes,
which look like pencils sticking up from the surrounding soil. These tubes
allow the tree to take in oxygen from the salty water. White flowers that are
rich in nectar appear year‐round on the tree. If you take a close look at one of
the black mangrove’s leaves, you may find salt crystals glistening on them.
Red Mangroves
Black Mangroves
White Mangroves
Buttonwood
Cayman Islands Native (Indigeneous) Plants
• Maiden Plum is native to the Cayman Islands, Cuba and
Hispaniola. In its natural state, it is not a common forest tree,
but once land is cleared or the forest/woodland canopy has
been removed and the sunlight has been let in, even along a
footpath, it quickly colonizes the cleared area, especially
pastures, old fields and the edges of trails.
• Learn to recognize and avoid touching this very common
small tree, It has distinctive, shiny, dark‐green compound
leaves, with 11‐17 tooth‐edged leaflets. Its caustic, acrid‐
smelling sap
turns blackish on exposure to the air.
• After contact, most people have an allergic reaction. Itching usually starts 24 hours later. Scratching can spread
the allergy to another area. Different remedies work with different people. It clears up in about 10 days.
Courtney before her allergic reaction to Maiden Plum.
My allergic reaction to Maiden Plum.
Maiden Plum
Endemic Species or subspecies• An endemic species or subspecies is one that has evolved in a
particular place or region. It does not occur naturally
anywhere else in the world.• The Blue Iguana is a Grand Cayman endemic species. It is a
herbivore. It does not occur naturally anywhere else in the
world. At the Botanic Park, they are a tourist attraction.
The Blue Iguana
Naturalized species• Some species introduced by human action to a location, area, or
region where it did not occur naturally (i.e. is not native)
becomes capable of establishing a breeding population in the
new location without further intervention by humans, but it does
not become a pest.
• The Green Iguana has been introduced from Central America. It
has become naturalized and is invasive. It is a tree‐dweller and a
herbivore.
The Green Iguana
Invasive Plants• Cow itch belongs to the Pea & Bean family.
• It is pantropical
and has become naturalized in Grand Cayman. This vine grows over other vegetation.
• When land is cleared, sometimes hundreds of seedlings will sprout and become invasive.
• The distinctive compound leaf has 3 leaflets, the mid‐ veins of the 2 side leaflets are off‐center.
• When ripe, the velvety‐brown seed pods are covered with stinging hairs which cause intense itching. They
cannot be washed off.
Human Interactions• Human Interaction has occurred in the Cayman Islands since
they were first settled in the 1730’s. In 1973 the population
was 12,000. In the last 35 years it has increased at least five
times over. Land has been cleared for buildings: houses,
apartments, hotels, offices, schools, churches, recreational
facilities and so on. Marl pits have been dug to get marl to
build up low‐lying areas. Natural buffers such as mangroves
have been cut down. Dry forests have been destroyed to make
way for development. Land is completely cleared, the building
is built and then its surroundings are landscaped with
imported plants because people want instant gardens.
Chemical fertilizers and pesticides are applied which may
cause pollution to our ground water and the sea.
Land is being cleared.
Photo credits
P. A van B. Stafford and Jennifer Godfrey