Sentences with phrase «predation levels»

Also, Crooks and Soulé seem (not enough detail is provided in their paper to be certain) to have used a simple average in their calculations, perhaps doubling true predation levels.

Taken together, these factors suggest that actual predation levels might be just a quarter of those suggested by Crooks and Soulé.

(Although Ellen Perry Berkeley [7] untangled this eight years ago — and has Fitzgerald on record stating that ABC's «interpretation» likely overstates predation levels by a factor of two or three — the claim is included in the 2011 version of ABC's Domestic Cat Predation on Birds and Other Wildlife.)

As a result — and as Berkeley pointed out — ABC's «interpretation» likely overstates predation levels by a factor of two or three.

While Lepczyk et al. emphasize the potential for under - estimating predation levels, they never consider the risk of over-estimating these levels — or their most obvious potential source of error: landowners» recollections of birds killed.

The Studies In the first study, Baker et al. distributed questionnaires to 3,494 households across a 4.2 km2 area of northwest Bristol (UK), and used responses to estimate cat ownership and predation levels (via prey returned home).

Porter also is interested in seeing whether oxygen played a role in predation levels through time.

Not exact matches

«But this level of criminal sexual predation is not something that I ever thought was going on.

What Griffin seems to have in mind here, are worlds that would be radically different from the world as it actually exists — worlds in which, for Instance, beings capable of high - level intrinsic values exist without predation, 4 or in which we and other animals could have existed without requiring food.

«On the island with the lower risk this kind of background choice, to improve their level of camouflage, is much less evident than on the island with high predation risk.»

First - time encounters thus resulted in initially high levels of predation.

He studied analyses of previous reef extinctions and accrued more and more evidence of the effects of changing sea levels, temperature stresses, predation by crown - of - thorns starfish and human - influenced changes in nutrient levels.

Ecologists Lauri Oksanen and Stephen Fretwell proposed that if we treat trophic levels as units, systems having four or more trophic levels may have more than one level representing predation.

Bringing together the observed macaque behavior and environmental conditions, we interpret the variation seen in macaque stone tool selection and shellfish characteristics on Koram and NomSao Islands as the result of a feedback loop driven by the level of predation pressure.

Once oxygen levels rose past this low level, predation likely provided a strong incentive for animals to get bigger and more complicated, and to develop new body plans.

First, we conducted growth trials at five temperatures crossed with two levels of predation risk (fish predator present versus absent) and measured growth rates, consumption rates, assimilation efficiencies, and production efficiencies of 107 individual damselflies.

«Any bird populations on the continents that could not withstand these levels of predation from cats and other predators would have disappeared long ago, but populations of birds on oceanic islands have evolved in circumstances in which predation from mammalian predators was negligible and they, and other island vertebrates, are therefore particularly vulnerable to predation when cats have been introduced.»

Something else often left out of the debate: predation — even at high levels — does not automatically lead to population declines.

The use of poison baits can reduce cat density, but even low levels of cat predation can exterminate threatened mammal populations, such as when cats killed at least seven bilbies reintroduced outside the Arid Recovery reserve in South Australia.

Furthermore, the question of whether cats are bad for birds at the population level involves a lot more than simple predation numbers.

In journal article after journal article, and book after book, I found cat - predation studies that were flawed by small sample size, samples that were not shown to be typical, unjustified generalizations, a failure to account for confounding factors, and a tendency to assume that predation of individual birds necessarily resulted in damage to bird populations at the species level.

Counting Cats and Counting Birds In both studies, the authors quantified the impact of cat predation on bird populations by comparing different levels of predation with different bird densities.

``... it is possible that cat predation was significantly affecting levels of recruitment and creating a dispersal sink for more productive neighboring areas.»

When it comes to relating predation to population levels, it's critical to understand the difference, and know the extent to which each type is occurring.

Compensatory and Additive Predation As I've discussed previously, even accurately predicted levels of predation can be dPredation As I've discussed previously, even accurately predicted levels of predation can be dpredation can be deceptive.

Barratt has shown that the actual predation rate, at this level, is less than half the rate predicted by cat owners.

Whatever ills one might associate (rightly or wrongly) with free roaming cats — whether public health concerns, wildlife predation, or anything else — it's clear that these problems can not be addressed in a comprehensive manner without the stabilization and eventual reduction in the level of the community cat population.

Much of that effort has involved the untangling of predation estimates based on indefensible sampling and extrapolation, and — more important — decoupling the implied relationship between predation and population - level impacts.

Another study conducted in a public park, this one in Alameda County, California, also reported low levels of apparent predation of birds (though researcher Cole Hawkins makes every attempt to suggest otherwise).

In the absence of predation, these lower - level species flourish because resources that support their energetic requirements are not limiting.

Monitoring indicated that, none returned to the islands.5 Today the occasional golden eagle visits the islands, but the level of predation on island foxes is negligible; all three island fox subspecies in the park are recovering rapidly.

Calf survival was poorer in those years due to lower food nutrition and higher levels of predation.

If that occurs, the premature removal of protection offered by subnivean birth lairs may expose young ringed seal pups to high levels of predation, which may negatively affect populations of ringed seals and the polar bears that depend on them for food.