Your typical tree squirrels- The North American Grey are now an established part of Great Britain's forest wildlife, with an astonishing population of 2.5 million. Because of this large population of tree squirrels in broadleaved woodland, significant damage to trees such as sycamore, beech, oak, pine, sweet chestnut, Norway spruce and larch is prevalent due to bark stripping. As a result, amenity value on the woodland goes down (1). 

In addition, the grey squirrel has a compelling impact on woodland birds in the area. Reports show that Nottinghamshire wood grey squirrels were responsible for nesting failures in 27% of nest boxes and that, on one farm in Norfolk, the control of grey squirrels reduced open nest predation from 85% to just 5-10%. In 2002 selective control of grey squirrel populations were implemented in many areas of the UK (1).

This species should be considered the most invasive, because the squirrels themselves have damaged property, and other wildlife. Essentially, it is primarily faulted by an easily attained food source. 

Mako Sharks are prized game fish- Even though its power, aggressiveness, teeth, and great speed make it a danger to humans. The world's affinity for shark fin soup and the flesh of the shortfin mako -especially in Asian markets- has led to its population decrease. The mako shark also has a low reproductive rate and a long life span, so as its population decreases, its much harder for them to reproduce fast enough to replenish the population it once had, therefore it is the most endangered (2).

In addition, the Mako Shark is killed because their fins have medicinal purposes, some as serious as treating cancer. However, this is primarily believed in Asian countries(2).

Mako sharks live in tropical and temperate offshore waters. This shark is seldom found in waters colder than 16 degrees Celsius. The mako us found worldwide. In the western Atlantic it can be found from Argentina and the Gulf of Mexico to Browns Bank off of Nova Scotia (2).

In many tests and observations, removal of starfish from its habitat was found to result in a rapid increase in the growth and biomass of a filter feeding mussel, which then managed to crowd out the other species and dominate the entire community(3). The starfish is keystone to its community because it is described as a keystone predator, and it initially prevented the mussel from achieving the full degree of community dominance that it was capable of developing on the basis of its competitive superiority over other species(4).

All in all, these starfish can greatly control a bivalve population that would otherwise explode(3). 

Starfish can be found in rock pools and on beaches. The habitat varies and includes coarse and shelly gravel and rock. Starfish are unusual in that it tolerates estuarine habitats. Its habitat range extends offshore for 400 meters(4).

When in flight the birds are said to make a noticeable hissing sound that emanates from the remiges on their wingtips. They have a wide-array of sounds that range from a popping noise caused by the snapping of their bills to a call that is compared to a distressed cat. This allows them to confuse their prey, and come in swift for an attack. They could also hide their faces and beaks while hiding inside their body, this gives them the coolest predator adaptation(5).

Guianan Cock-of-the-Rocks are found amongst the mountainous regions of northern South America: Guyana, Suriname, French Guiana, Columbia, Venezuela, and Amazonian Brazil. The preferred habitat is humid forest near rocky outcrops. This species has a large range that covers about 20,000 km2 (5).

When exposed on a low tide, this beauty squeezes out its water and recoils into something resembling a small orange brain. Add a little water though, and BOOM! They expand to a lovely plume, feeding on the plankton that wash past. Now for the even cooler part… They aren’t really a single living creature with a body and some sort of feathery feeding appendages (like a feather duster worm or plumose anemone) (7).They’re related to corals, which have many tiny polyps that build and add onto the calcium carbonate base they all share. The hundreds of polyps in a sea pen have different functions but work together as a single organism(6). The big “stem” of the pen is made up of one enormous polyp that no longer has tentacles and formed a big bulb at the bottom that it uses to fix itself in the sediment. The feathery parts of the pen that branch out from the stem are made up of tiny polyps that feed on plankton, intake water or produce sperm and eggs(6). 

Orange sea pens may fall prey to several species of sea stars, but are the primary prey of the striped nudibranch (Armina californica). Alas, the pen is not mightier than the slug. In addition,they’re bioluminescent at night! Which indeed gives them the coolest prey adaptation.

The orange sea pen's habitat is the plain old sandy seafloor in tropical and temperate waters worldwide. Its range covers the Gulf of Alaska to southern California on sandy or muddy bottoms, in depths from 45 feet (13.7 m) to 225 feet (68.5 m) (8).