Seal hunters will be allowed to kill 275 000 animals this season. This is
well within the “replacement yield” of 286 700 that a 1994 population census
suggested could be taken without causing a decline in population. “The herd will
not be threatened by this year’s harvest,” said David Anderson, the fisheries
and oceans minister.

However, research by David Lavigne, director of the International Marine
Mammal Association, reveals that when those animals that were shot but whose
bodies were not retrieved are taken into account, the number of seals killed in
each of the past two years is between 420 000 and 550 000. “The government has
stated previously that its objective is a stable seal population,” says Lavigne.
“My analysis is that it has not been achieving its objective for the past three
˛â±đ˛ą°ů˛ő.”

John Harwood of Britain’s Sea Mammal Research Unit says the number of seals
“struck and lost” has risen since restrictions on killing young were introduced
because older animals now make up a higher proportion of the catch—and
they are more likely to be shot in the water.

Environmental groups maintain that the government should have erred on the
side of caution, particularly in the light of the collapse of stocks of cod and
other fish. But Gary Stenson, a scientist with the Department of Fisheries and
Oceans, says that new research from Greenland suggests the seal population would
sustain a cull significantly greater than the replacement yield.

It’s long been known that heavy manual labour may cause progesterone levels
to drop, and ovulation and periods to stop. However, it was unclear whether this
was a response to the work or to the body’s resulting lack of energy.

To resolve this, Grazyna Jasienska and Peter Ellison of Harvard University
studied 20 women in a Polish agricultural community who work hard during the
summer months. Even though they compensated by eating more in the summer, their
progesterone levels still dropped. This suggests that the work itself suppresses
the reproductive cycle.

The researchers offer two possible explanations for this. First, it’s
unlikely that extra food was freely available during our evolutionary past, so
increased workloads would almost always produce a shortage of energy. “Switching
off” reproductive systems would spare women the extra burden of pregnancy and
give a woman an evolutionary advantage. Alternatively, a high turnover of energy
expenditure and intake may somehow constrain a woman’s ability to allocate
energy to reproduction (Proceedings of the Royal Society B, vol 265, p
673).

Exercise is known to lower the risk of breast cancer, probably by lowering
sex hormone levels. The researchers suggest that this may also be why the
incidence of breast cancer is lower in the developing world. “If we are right,
we can predict that as lifestyles change in the developing world and physical
workloads decrease, the risk of breast cancer will increase,” says Ellison.

Alan McNeilly, a reproductive biologist at the University of Edinburgh, says
the study is thought provoking. The link between lifestyle and the rate of
reproductive cancer is tenuous, he says. “But it’s not unreasonable,” he adds.

A single cuckoo chick in a reed warbler’s nest will eject its hosts’ young
and be raised alone. When warblers raise their own brood, they adjust the
feeding rate to the number of chicks present. But a cuckoo chick somehow
commands five-star service, and persuades its hosts to bring it as much food as
they would give four of their own chicks.

Some researchers have speculated that it is the cuckoo chick’s size that
stimulates the reed warblers to provide bigger feeds. Nick Davies, Rebecca
Kilner and David Noble of Cambridge University tested this idea by putting
blackbird chicks, which are about the same size as their cuckoo counterparts, in
the reed warblers’ nest.

At first they found that the blackbird chicks were given much less food than
the cuckoo. But when the researchers installed loudspeakers broadcasting the
rapid squeaky begging call of the cuckoo chick, the hosts brought as much food
to the young blackbirds as to a cuckoo chick (Proceedings of the Royal Society
series B, vol 265, p 673). This cry, says Davies fools the unsuspecting birds.
“It sounds remarkably like a whole brood of reed warblers,” he says.

Anders Møller, a behavioural ecologist at Pierre and Marie Curie University
in Paris, says the work shows what a large part deception plays in the cuckoo
lifestyle. Cuckoos are known to produce eggs that mimic the appearance of their
hosts’. “It demonstrates that mimicry occurs also at the chick stage,” he says.

Diamond told the British Ornithologists’ Union annual conference in Edinburgh
this month that he found many birds, especially parrots, feeding on soil exposed
by landslides in the dense forests of the island of New Guinea. Some other
animals are already known to eat soil, which is thought to provide them with
vital minerals.

However, the soil the parrots eat contains smaller amounts of essential
minerals than the fruit that makes up most of their diet—and “less sodium
than the Los Angeles water supply”, says Diamond. The particles in the soil were
too small to be put to use grinding food in the birds’ guts, and it was
ineffective in buffering the acids that cause indigestion.

So why were the birds so hooked on soil? Diamond suspected it may help them
to tolerate a diet of seeds. Plants often encase their seeds in hard,
indigestible coatings and lace them with toxic quinines and tannins to protect
them from fruit eaters tempted by the nutrients within. Parrots can breach the
physical defences with their strong, dexterous bills, but could still be
vulnerable to the toxins.

Diamond found that the soil binds to quinines and tannins in the same way
that milk proteins bind to tannins in tea. This renders harmless the chemicals
in the seed coating, allowing parrots to feed on seeds without being poisoned.
Diamond says that, taking weight into account, parrots can consume 100 times as
much quinine as humans before it is detectable in the bloodstream.

For 3 billion years after the appearance of life on Earth, the world was
dominated by relatively simple, single-celled organisms. Around 900 million
years ago, something kick-started the transition to multicellular life. Why that
happened has been debated for decades. One idea was that natural selection
favoured cells that clumped together because they would be too big a mouthful
for single-celled predators.

To test this, Martin Boraas and his colleagues at the University of Wisconsin
in Milwaukee studied cultures of the green alga Chlorella vulgaris. The
researchers had already shown that populations of the alga will remain
single-celled for more than two decades as they multiply, except for the
occasional appearance of loose clusters of the cells.

However, when the scientists inoculated the cultures with Ochromonas
vallescia, a predatory single-celled flagellate, it was a different story.
The algae initially went into decline, but then recovered. At this stage the
alga population included colonies made up of anything from four to hundreds of
cells, as well as single cells.

Sixteen days after inoculation, during a second cycle of flagellate growth
and Chlorella decline, the colonies persisted while the single cells
dropped in frequency to less than 1 per cent of all cells in the culture. The
number of cells in the algal colonies then gradually declined until they reached
a steady state only 10 to 20 generations after the predator was introduced. At
this point, the bulk of the Chlorella cells were part of eight-cell
colonies.

The researchers’ observations confirmed that while the flagellate could
ingest single cells and young colonies, mature colonies were simply too big. So
predation conferred a selective advantage on the rare mutation that for some
reason caused the algal cells to stick together.

“Our study provides evidence of what we think is a reasonable hypothesis for
one possible origin of multicellularity: survival or resistance to ingestion,”
says Boraas.

During normal cell division, Chlorella divides into between 2 and 16
daughter cells, which then split from the mother cell wall. But in colonies, the
cell wall remains intact, holding the daughter cells together. When the daughter
cells divide, they bud off from the parent colony, making the multicellular
colonies self-replicating units. A similar process might have set the scene, 900
million years ago, for the subsequent evolution of complex multicellular
animals.

That the initial large colonies gradually give way to the eight-cell pattern
probably reflects the trade-off between the pressures of predation and of
maximising nutrient uptake, as cells within a large colony have less surface
area exposed to the nutritive medium. When unicells and colonies were cultured
in the absence of the predator, the unicells again became dominant (
Evolutionary Ecology, vol 12, p 153).

The study provides “remarkable present-day evidence that predation pressure
induces multicellularity”, says Nick Barton, an evolutionary biologist at the
University of Edinburgh. “This is a nice example of how studying populations now
can tell us about our distant past.”

Lynn Margulis and Dorian Sagan have “taken the liberty of speaking out on
issues widely considered taboo in scientific circles.” Thus they introduce
Slanted Truths—Essays on Gaia, Symbiosis, and Evolution
(Springer-Verlag, ÂŁ16.99/$27, ISBN 0387949275). Margulis is no
stranger to controversy. Her work on the role of bacterial symbiosis in the
evolution of eukaryotic cells was long ridiculed—but it is now generally
accepted that organelles, such as mitochondria and chloroplasts, are indeed
bacterial symbionts.

“Symbiosis and Individuality” joins “Memoirs”, “Gaia”, and “Evolution and
Evolutionists” to make up the four sections of this collection of essays
covering the period from 1956 to 1996. Many of the essays are cowritten by
Margulis with her son Dorion Sagan, and some with others, such as James
Lovelock. Subjects range from the colonisation of space to the problems of
teaching and funding science.

If there is a common theme, it is the importance of microorganisms, and
especially bacteria, in the evolution of life and the ecology of our planet.
This is hard to ignore considering that we are products of bacterial symbiosis.
Margulis also argues that microorganisms are responsible for the self-regulating
atmospheric system postulated in Lovelock’s Gaia hypothesis—a “taboo” in
many circles and certainly not (yet?) embraced by the scientific community.

Slanted Truths is packed with original ideas and new angles on old
ones. I wonder how many will be proved right.

Bryant Furlow and his colleagues at the University of New Mexico in
Albuquerque say their research shows that the influence of genes on cognitive
ability may be indirect. Rather than determining intelligence per se, the genes
involved may instead affect the ability of the developing body and brain to
withstand environmental stresses.

The more vulnerable a growing human is to stresses such as malnutrition,
infection or pollution, the more lopsided it will become. So the researchers
measured “fluctuating asymmetry” (FA), or the degree to which bilateral traits
such as ears, hands and eyes deviate from the symmetrical, in 240
undergraduates. They found a “modest” negative correlation between FA and IQ as
measured by a psychometric test called the Cattell’s culture fair intelligence
test. The findings are published in this month’s Proceedings of the Royal
Society B (vol 264, p 823).

“Proof of a causal relationship between developmental stress and adult IQ is
further down the road,” says Furlow. But the team has put forward two possible
explanations for the effect. Developmental stress may compromise the integrity
of the brain’s structure, reducing “neural efficiency” at tasks such as
information processing. An asymmetrical body may also be more “metabolically
inefficient”, requiring more energy to perform its basic functions, so that
energy is diverted away from cognitive tasks.

“The heritability of IQ may thus be in genetic factors related to
developmental instability,” says Randy Thornhill of the New Mexico team. If so,
the social implications of this work could be profound. If genetic weaknesses in
development could be overcome by improved prenatal and neonatal medical care and
nutrition programmes, then IQ should be boosted, particularly at the lower end
of the spectrum. “The door is open to create very smart kids if that is what is
desired,” says Thornhill.

Andrew Read, an evolutionary ecologist at the University of Edinburgh
describes the work as “stimulating”. But, he adds, a correlation between
symmetry and IQ does not represent a causal link. “At this stage, it is not
clear whether it says anything about genetic influences.”

Since 19 May, 81 corpses have been washed ashore in Western Sahara and
Mauritania. They come from the largest single population of the seals,
Monachus monachus, estimated last year to account for 270 of the world
population of around 600. About 20 seals live on the Desertas Islands near
Madeira, off the coast of northwest Africa, while smaller populations are
scattered throughout the Mediterranean.

From the numbers of animals hauling themselves ashore in caves on the
Atlantic coast, scientists estimate that up to 150 seals may have been killed by
the toxic bloom. “This is a heavy blow and a sad event,” says Peter Reijnders of
the Institute for Forestry and Nature Research in Wageningen, the Netherlands,
who chairs the steering committee of the European Union monk seal project.

Postmortems suggest that the dead seals were exposed to toxins produced by
single-celled organisms called dinoflagellates. Seawater samples collected near
the monk seal caves contained more than 2000 dinoflagellate cells per litre.

An as yet unidentified virus also showed up in the posmortems. Marine mammals
can succumb to distemper, but scientists believe that it is not the primary
cause for the latest deaths, which did not affect pups and juveniles; viral
diseases usually hit pups hardest. But as a precaution, the EU team plans to
vaccinate survivors against the phocine distemper virus “as soon as the
behaviour of the colony, which at present is strongly disturbed, returns to
normal”, says Alex Aguilar of the University of Barcelona.

The EU team is now deciding whether to remove the survivors from the affected
area to caves or beaches where they could be held until dinoflagellate
concentrations in their usual haunts return to a safe level. The danger is that
this could stress the disturbed animals further. “A final decision will be made
this week,” says Reijnders.

There are now fewer than 5000 wild dogs, Lycaon pictus, on the
plains of Africa. Some estimates put the figure as low as 3000. To help save the
remaining animals, scientists have fitted some dogs with radio collars to track
their movements, and have vaccinated many of them against rabies. Unfortunately,
for both procedures the dogs must be darted with anaesthetic and handled.

This has been the centre of a bitter controversy since Roger Burrows of the
University of Exeter suggested that handling the dogs contributed to an outbreak
of disease that nearly wiped them out in Tanzania’s Serengeti National Park in
1991. In a series of papers, Burrows argued that handling the dogs boosts levels
of stress hormones that suppress the immune system, leaving the dogs unable to
fight off dangerous viruses (see “Wild at Heart”, żěè¶ĚĘÓƵ, 19
November 1994, p 34).

Until now, no one had compared levels of stress hormones in dogs that were
handled and those that were not. But Scott Creel and Nancy Creel of Rockefeller
University in New York and Steven Monfort of the US National Zoological Park’s
Conservation and Research Center in Fort Royal, Virginia, have done just that
for dogs in the Selous Game Reserve, also in Tanzania.

As part of the Frankfurt Zoological Society’s Selous Wild Dog Project, the
Creels and Monfort measured levels of the stress hormone corticosterone in
samples of the dogs’ faeces collected over two years. They found no differences
between dogs that had never been handled and those that had been darted,
vaccinated against rabies and fitted with a radio collar.

Dogs handled during the study also showed no obvious jump in corticocosterone
levels. And there was no relationship between levels of corticosterone in the
faeces of dogs wearing collars and the time that elapsed since they were handled
(Conservation Biology, vol 11, p 544). “We detected no effect of
collaring,” says Scott Creel.

Burrows is not convinced, however. He argues that the Selous researchers
selected “vigorous individuals” for collaring. This would mask any effects of
handling, Burrows claims, because strong, healthy dogs will be less prone to
stress.

Burrows points to studies by his group which suggest that dogs that leave
their own pack and join another—most of which tend initially to be low
down the pecking order—respond badly to handling. “Survival of those
handled after joining a new pack is significantly reduced,” he says.

However, the Selous researchers counter that their research shows that it is
the top dogs, not those as the bottom of the social pile, that are more stressed
(“Stressed out”, żěè¶ĚĘÓƵ, 5 October 1996, p 38).

Wildlife biologists hope that a definitive ruling on the merits of collaring
will come from an action plan to protect wild dogs commissioned by IUCN, the
World Conservation Union. Rosie Woodroffe of the University of Cambridge, the
plan’s author, says that she will not comment until details of her scheme are
made public later this year.