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California condors are the largest birds in North America,
and they’re also critically endangered.
At one point in the 1980s, there were fewer than
30 individual birds in the entire species.
Since 1988, a captive breeding program has bolstered
those numbers to over 1000.
That doesn’t leave a lot of genetic diversity to work with, so the scientists in charge
of that program have been carefully selecting mates to create the
most diverse population they can.
But last week, we learned that a couple of female
condors took matters into their own wings.
They laid eggs that developed into offspring without any help from a male.
The details are in a new paper out last week in the Journal of Heredity.
These researchers report the first two known
cases of parthenogenesis in California condors.
Parthenogenesis is a form of reproduction where the female produces eggs that
develop into embryos without ever being fertilized.
Some species of insects and other invertebrates have evolved
to only reproduce through parthenogenesis.
Some other species can reproduce in this fashion,
but only do so when a male just can’t be found to fertilize the eggs.
This has been reported in snakes, lizards, and turkeys.
Though this is probably one of the most solid reports in a bird so far.
The genomes of the birds in the condor breeding program are carefully monitored,
so the researchers were able to work backwards to figure out what happened.
And here’s the weird thing: the two condor females had been housed with males,
and had laid eggs with them before. It wasn’t like a fertile mate wasn’t available.
Which makes this the first time that parthenogenesis has ever been reported in any
bird species where we know for sure the female had access to a mate.
This discovery could be big news for the conservation of the species.
For one thing, if all you need is one one female bird to found a breeding population,
that could help their range expand faster.
That’s because these offspring aren’t female like their parents, thanks to the way
that sex chromosomes work in birds.
Females have one Z and one W chromosome, while males have two Z’s.
These parthenote chicks would have gotten a Z from their female parent, which got
duplicated at some point to make them ZZ -- so they are male!
Which means that theoretically, you now have males and females that can
reproduce in the conventional way from as few as one individual.
This could also be a way of getting fatal gene mutations out of the gene pool.
The exact way this goes down is a bit complicated, but basically, these chicks have
two sets of chromosomes, but a lot of the versions of genes, or alleles, on those
two chromosomes end up being identical.
When the offspring get one allele from each parent, there’s a decent chance they
will be different from each other.
If one of those alleles is harmful or even fatal to the bird, they might get a healthy
one from the other parent and be ok.
But because the genetic diversity in condors is so low,
that chance is lower than usual.
Either way, that harmful allele is still lurking in their
genome to potentially pass on.
Parthenotes, however, are extremely likely to get a double whammy,
getting both versions of a harmful allele from their single parent.
This may very well kill the bird.
Which is bad for the bird, but good for the population overall,
because it can’t pass those harmful alleles on if it is dead!
Which makes parthenogenesis a potential double-edged sword, and ultimately,
we don’t know yet whether it’s helping or hurting.
In fact, neither chick survived to have offspring of their own.
Even so, these parthenogenetic parents raise questions about what other species
could be reproducing through parthenogenesis,
and what that capability might mean for conservation efforts.
And California condors aren’t the only big, charismatic animals
we’re still learning more about.
New research published this week in Nature suggests
that whales are a lot hungrier than we knew.
Like three times hungrier.
An international team of researchers set out to figure out just how much large
baleen whales, like blue whales and humpback whales, eat.
These whales take gulps of water and then force it back out through tough bristles
in their mouths, expelling the water while filtering out
tiny fish and krill for them to chow down on.
The researchers attached GPS devices to the whales to monitor their movements
and figure out when they were eating.
They also photographed the whales with drones to measure
how big they were, and by extension, how much they could eat.
In places where they observed whales eating,
they would measure the population of prey species like krill.
And with that information, the researchers were able to
estimate how much the whales eat.
And it turns out that whales eat a lot.
An eastern North Pacific blue whale can consume 16 metric tons of krill per day.
Previously, scientists thought that all of the whales in the region of the
Pacific Ocean from Canada to Mexico eat about
two million metric tons per year combined.
This finding suggests that they actually eat more than six million tons of food.
And while that’s impressive, understanding how much whales eat is really
important for understanding ocean ecosystems.
Because eating more food means pooping more poop.
And whale feces contains a ton of iron, which is a critical nutrient for phytoplankton.
And conveniently, krill feed on phytoplankton.
So the whales eat the krill and then poop out iron near the water’s surface, which
helps phytoplankton grow, which krill colonies eat, and then the cycle begins again.
Which also explains why, when whale populations diminished due to commercial
whaling, krill populations actually shrank with them.
Even though fewer whales were eating them.
Since phytoplankton also consume carbon dioxide through photosynthesis,
restoring whale populations could actually increase the
amount of CO2 that gets pulled out of the atmosphere.
In fact, the researchers think that when whale populations were at their peak, they
probably did as much for atmospheric carbon removal as forests.
So it turns out that baleen whales don’t just have massive appetites.
They, and their poop, are massively important to the global carbon cycle.
Thanks for watching this episode of SciShow, and a huge thanks to this month’s
President of Science, Matthew Brant!
Your support means a lot to us, and we really couldn’t do it without your help.
If you’d like a shot at becoming the President of all science yourself,
you can get started at patreon.com/scishow.
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