Anthropogenic Threats

Urbanisation and marine mammal threats

What was the historical impact of whaling on whale populations?

Whaling led to massive population declines, especially in the 1800s when whale oil, baleen, and spermaceti were in high demand.

What products were obtained from whales?

Whale oil (lighting, machinery), baleen (corsets, carriages), spermaceti (candles), ambergris (perfume), and blubber (oil).

How did modern whaling increase the scale of exploitation?

Whales were processed at sea, allowing for greater efficiency and range.

What was ambergris used for?

Perfume and cocktails; it comes from sperm whales and may protect their digestive tracts from squid beaks.

Why was whale 'bone' or baleen valuable?

It was strong yet flexible, used for corsets, umbrellas, and carriage springs—known as "plastic of its time."

What was spermaceti?

A waxy substance from the sperm whale's head used for high-quality candles.

How did sealing compare to whaling?

It was nearly as extensive, targeting haul-out sites and leading to rapid population collapse.

Why were sealing targets easy to exploit?

Seals gather in large numbers, making them easy to hunt in high volume.

What species was hunted to extinction due to anthropogenic pressure?

The Baiji, a river dolphin from China, which went extinct due to pollution and development.

What is threatening the vaquita today?

Bycatch in local fishing nets, especially from illegal totoaba fisheries in the Gulf of California.

What is the totoaba?

An endangered fish whose swim bladders are prized, indirectly threatening the vaquita via bycatch.

What limits recovery of North Atlantic right whales (NARW)?

Human-caused mortality, especially adult female deaths from fishing gear entanglement and ship strikes.

What is the main cause of known NARW mortality?

Entanglement in fishing gear and vessel collisions.

How can shipping be adapted to reduce whale deaths?

By changing shipping lanes and enforcing speed limits in known whale habitats.

What shipping speed is recommended to reduce whale strikes?

10 knots in areas where whales are present.

How effective are reduced breaking strength (RBS) ropes?

RBS ropes under 7.56 kN could reduce whale deaths and injuries by over 70%.

What is the estimated recovery rate of some whale populations?

As low as 3% annually, even with protections in place.

Why is prey availability important for whale recovery?

Insufficient prey affects calf survival and limits population growth.

Why is data inconsistency a challenge in conservation?

Some species have excellent data while others are poorly monitored, making targeted action difficult.

What factors make some species easier to protect?

Accessibility and distinctiveness, which make population tracking and identification easier.

What example demonstrates recovery after severe decline?

South African fur seals and humpback whales recovered dramatically from low population levels.

What determines the potential for recovery?

The extent of historical decline and current environmental conditions.

Why is urbanisation ecologically important?

It's a global, ongoing phenomenon that alters ecosystems and affects biodiversity and human health.

What are three reasons urbanisation matters?

It's expanding worldwide, affects human disease risk, and alters ecosystems and wildlife health.

How does urbanisation affect biodiversity?

It filters out sensitive species, leading to reduced overall diversity and dominance by generalists.

Which species tend to succeed in urban environments?

Generalists with high dispersal abilities and behavioural flexibility.

What are common traits of urban-adapted animals?

Flight ability, broad diets, flexible behaviour, and inherited tolerance to disturbance.

What behavioural change is often seen in urban birds?

Singing at unusual times like night, and reduced migration due to milder conditions.

How do we detect adaptation to urban environments?

Through behavioural observation and genetic sequencing.

What has been observed in urban great tits?

Selection for increased cognitive abilities and problem-solving traits.

How does human food affect urban wildlife?

It has higher starch content, which may influence digestive physiology and foraging behaviour.

What was the impact of urbanisation on blue tit reproduction?

Fledging success was lower in urban areas, especially in harsher years.

What year showed the greatest negative effect of urbanisation on blue tits?

2015, a cold and late season, saw sharp declines in urban reproductive success.

What questions were raised from urban bird studies?

Are urban populations self-sustaining? Is there a net movement from rural to urban populations?

Why is resource limitation a concern in urban areas?

There's less natural food like caterpillars, making survival and reproduction more fragile.

Why doesn't reproductive success equal population sustainability?

Most fledglings die young; high birth rates don't always mean population growth.

What percent of blue tit fledglings survive their first year?

Only about 10%, with further reductions into adulthood.

Why might urban bird populations depend on immigration?

Without incoming individuals from rural areas, urban populations could decline.