BIOSCI 109: Lecture 7 - Community Interactions II: Predation

Predation

An exploitative interaction where a predator is benefited and a prey is harmed/killed.

Prey and predator aren't as tightly coevolved due to them being able to quickly adopt different behavioirs and adaptions.

Most predators are generalists, being able to hunt anything. Some are specialists with specific adaptations. All predators have adaptations to help them hunt better

Cyclical Predator-Prey Pattern

As prey populations increased, so did predator populations. More predators could lead to the extinction of prey populations, typically meaning less food overall.

However, in nature, prey are typically able to avoid extinction.

How Prey Avoid Extinction

In natyre where there's a lot of habitats, prey can disperse quickly as well have develop barriers/refuges against predators.

This barriers are things such as behavioural defences, morphological defences, or using their physical surroundings to their advantage.

Doing this gives prey enough time to recover from any damage predatoes may have caused.

Predator Impacts on Prey

The impact predators have on prey depends on the adaptations prey may have. Typically, prey would adapt to the natural predators in their natural environments.

For example, Aotearoa had mainly flying avian predators. So the prey here (other birds, reptiles, etc) adapted to staying closer to the ground, having duller colours, and freezing when predators were around.

But when mammalian predators were introduced, the same adaptations the prey had no longer worked against the new threats.

Predation typically affects younger populations more due to them being easier targets. So they can change the age distribution of a population and make it harder for them to recover due to no/less recruitment.

They also tend to change the distribution of prey. Prey may move to places where the predators aren't occupying. An example is our native galaxiid where are only found where trout aren't.

Introduction of Invaisve Predators

Invasive predators are harmful to native prey everywhere but tend to affect island populations more. Island organisms tend to have more specific and narrow ranges, niches, and adaptations.

When new predators are introduced, native prey typically don't have the right defences against them.

Invasive predators also affect human populations too typically being a nuisance (eating crops, invading homes, etc)

Climate change has also increased the habitat ranges of many invasive predators, allowing them to move and survive into new areas. For example, Aotearoa's milder temperatures are a lot more warmer, being more bearable for outsiders.

Elimination of Invaisve Predators

A one-off but very expensive and difficult process of completely removing an invasive predator with efforts focusing on no re-introductions.

Typically done on smaller areas/islands due to how the isolation and size makes it easier to control introductions.

Control/Supression of Predators

A continual process with continuing costs of keeping invasive populations to a minimum where preys can survive and thrive.

This requires us to have extensive data on the impacts of the invasive predators. It is like flatenning the curve, the predators are still there, just not as big of a problem.

Predator-Free NZ

A goal to completely eliminate some of NZ's most damaging invasive predators by 2050.

This strategy is starting with smaller islands due to their size and isolation. Then there'll be a rolling front towards mainland, creating more and more suitable habitats for native species to settle and establish themselves. It focuses on the hope rather than despair when it comes to invasive predators.

However it has some challenges:

• Extremely costly and time costly
• Ethical worries about the tools being used, science being applied, and the implication on the ecosystem.
• Governments tend to focus on other pressing issues (economy, healthcare, etc)
• Extremely hard to track and eliminate last few predators to ensure they can't recover.
• Taking away some invasive predators may have unexpected ecological effects (competitor release).