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Department of Zoology

 

Monitoring the Meerkats of the Kalahari

Cam ac uk zoology department feed - Fri, 16/07/2021 - 08:55

Getting close was a challenge. Cracking it was key to an incredible 30-year study of the wild meerkats of the Kalahari. 

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Climate changed the size of our bodies and, to some extent, our brains

Cam ac uk zoology department feed - Thu, 08/07/2021 - 10:21

An interdisciplinary team of researchers, led by the Universities of Cambridge and Tübingen, has gathered measurements of body and brain size for over 300 fossils from the genus Homo found across the globe. By combining this data with a reconstruction of the world’s regional climates over the last million years, they have pinpointed the specific climate experienced by each fossil when it was a living human.

The study reveals that the average body size of humans has fluctuated significantly over the last million years, with larger bodies evolving in colder regions. Larger size is thought to act as a buffer against colder temperatures: less heat is lost from a body when its mass is large relative to its surface area. The results are published today in the journal Nature Communications.

Our species, Homo sapiens, emerged around 300,000 years ago in Africa. The genus Homo has existed for much longer, and includes the Neanderthals and other extinct, related species such as Homo habilis and Homo erectus.

A defining trait of the evolution of our genus is a trend of increasing body and brain size; compared to earlier species such as Homo habilis, we are 50% heavier and our brains are three times larger. But the drivers behind such changes remain highly debated.

“Our study indicates that climate - particularly temperature - has been the main driver of changes in body size for the past million years,” said Professor Andrea Manica, a researcher in the University of Cambridge’s Department of Zoology who led the study.

He added: “We can see from people living today that those in warmer climates tend to be smaller, and those living in colder climates tend to be bigger. We now know that the same climatic influences have been at work for the last million years.”

The researchers also looked at the effect of environmental factors on brain size in the genus Homo, but correlations were generally weak. Brain size tended to be larger when Homo was living in habitats with less vegetation, like open steppes and grasslands, but also in ecologically more stable areas. In combination with archaeological data, the results suggest that people living in these habitats hunted large animals as food - a complex task that might have driven the evolution of larger brains.

“We found that different factors determine brain size and body size – they’re not under the same evolutionary pressures. The environment has a much greater influence on our body size than our brain size,” said Dr Manuel Will at the University of Tubingen, Germany, first author of the study.

He added: “There is an indirect environmental influence on brain size in more stable and open areas: the amount of nutrients gained from the environment had to be sufficient to allow for the maintenance and growth of our large and particularly energy-demanding brains.”

This research also suggests that non-environmental factors were more important for driving larger brains than climate, prime candidates being the added cognitive challenges of increasingly complex social lives, more diverse diets, and more sophisticated technology.

The researchers say there is good evidence that human body and brain size continue to evolve. The human physique is still adapting to different temperatures, with on average larger-bodied people living in colder climates today. Brain size in our species appears to have been shrinking since the beginning of the Holocene (around 11,650 years ago). The increasing dependence on technology, such as an outsourcing of complex tasks to computers, may cause brains to shrink even more over the next few thousand years.

“It’s fun to speculate about what will happen to body and brain sizes in the future, but we should be careful not to extrapolate too much based on the last million years because so many factors can change,” said Manica.

This research was funded by the European Research Council and the Antarctic Science Platform.

Reference

Will, M. et al: ‘Different environmental variables predict body and brain size evolution in Homo.’ Nature Communications, July 2021. DOI: 10.1038/s41467-021-24290-7

The average body size of humans has fluctuated significantly over the last million years and is strongly linked to temperature. Colder, harsher climates drove the evolution of larger body sizes, while warmer climates led to smaller bodies. Brain size also changed dramatically but did not evolve in tandem with body size.

Our study indicates that climate - particularly temperature - has been the main driver of changes in body size for the past million years.Andrea ManicaHuman fossils illustrating the variation in brain (skulls) and body size (thigh bones) during the Pleistocene.


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Conserving an endangered butterfly into the future

News from this site - Fri, 18/06/2021 - 08:20

Conserving an endangered butterfly into the future: long term requirements of the Duke of Burgundy Matt Hayes is a research assistant in our Museum of Zoology, looking at historical museum specimens, investigating how losses from the past can help guide conservation of the future. Over the past few years, he has worked...

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The conservationist helping us to make better decisions

Cam ac uk zoology department feed - Fri, 04/06/2021 - 11:26

Bill Sutherland has started a revolution in conservation. Put simply he’d “like us to stop doing the things that we know don't work and do more of the things that do” – and with global collaborators is building the tools to help people achieve this.

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Dive bombing Killer flies are so fast they lose steering control

Cam ac uk zoology department feed - Thu, 27/05/2021 - 09:20

These are the findings of a study by researchers at the Universities of Cambridge, Lincoln, and Minnesota, published in the Journal of the Royal Society Interface

Killer flies (Coenosia attenuata) perform high-speed aerial dives to attack prey flying beneath them, reaching impressive accelerations of up to 36 m/s2, equivalent to 3.6 times the acceleration due to gravity (or 3.6g). This happens because they beat their wings as they fall, combining the acceleration of powered flight with the acceleration of gravity.

This is an impressive feat: diving Falcons, the fastest animals that predate in the air, achieve much lower accelerations of only 6.8m/s2. Falcons dive by folding their wings and simply letting gravity accelerate them towards their prey.

For the tiny Killer fly though, the high speeds achieved in aerial dives could come as a surprise - because the researchers think the fly doesn’t take the effect of gravity into account when diving to intercept a target. 

To get their results, the researchers built a transparent ‘flight arena’ and flew a dummy prey target through it at constant velocity. Killer flies were filmed with high speed video cameras as they attacked the target, and the researchers watched the footage back in slow motion - using this data to reconstruct the entire attack sequence in 3D. 

The study found that Killer flies reached much higher accelerations in flight when taking off from the ceiling of the arena, compared to from the floor or walls. The flies beat their wings at a similar rate wherever they launched from, indicating that their flight speed is determined by a combination of wing power and gravity. 

“When Killer flies took off from the floor or walls of the arena, they moved at the time when they could take the shortest path to the target. But they couldn’t manage that when they took off from the ceiling because the high acceleration caused by gravity changed the expected flight path,” said Sergio Rossoni, a PhD student in the University of Cambridge’s Department of Zoology and first author of the paper.

By diving with super-high acceleration the Killer fly sometimes catches its target prey extremely quickly, but it often misses because its speed makes it challenging to change course mid-dive if the prey moves. But even if the fly doesn’t land on target, the dive quickly reduces its distance from the prey so it can keep sight of it while making the final manoeuvers to catch it.

 

 

The researchers think the effect of not accounting for gravity during downward dives might be compensated by another advantage. High speed dives force the potential prey to change direction as the attacker approaches, but to do this the prey has to slow down - making it easier to catch.

Insects that hunt in the air usually attack their prey upwards, because the contrast of the prey against the sky makes it easier to see. Killer flies are unusual insect predators in this respect; hunting downwards against a visually cluttered ground, using eyes that have only coarse resolution, is more difficult. 

“This research into miniature flies helps us understand what shortcuts are acceptable when survival depends on fast decisions and accurate actions, but the sensory capabilities and processing power of the predator are heavily constrained,” said Professor Gonzalez-Bellido at the University of Minnesota, who led the study.

This research was funded by the Air Force Office of Scientific Research, the Biotechnology and Biological Sciences Research Council and the Royal Society.

Reference
Rossoni, S. et al: ‘Gravity and active acceleration limit the ability of killer flies (Coenosia attenuate) to steer towards prey when attacking from above.’ J.R.Soc.Interface, May 2021. DOI: 10.1098/rsif.2021.0058

 

Killer flies can reach accelerations of over 3g when aerial diving to catch their prey – but at such high speeds they often miss because they can’t correct their course.

The high acceleration caused by gravity changed the flies' expected flight path when they took off from the ceilingSergio RossoniS.T.FabianKiller fly


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These birds will soon go extinct. But their disappearance need not be in vain.

Cam ac uk zoology department feed - Wed, 19/05/2021 - 20:11

The White-tailed Swallow and Ethiopian Bush-crow are living in ‘climatic lifeboats’ with their tiny ranges restricted on all sides by temperature and rainfall patterns. Even under moderate climate warming, models predict a severe loss of suitable climate for these birds within the next 50 years - dramatically heightening their risk of extinction.

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Roger Northfield

News from this site - Wed, 19/05/2021 - 09:42

The Department is sorry to announce that our former colleague Roger Northfield died last Thursday evening. Roger joined the department just one month after his 16th birthday, in 1956, as a Junior Assistant. He soon became responsible for all laboratory insect cultures, receiving the accolade “best in his field” by the...

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Congratulations to Professor Rebecca Kilner, FRS

News from this site - Tue, 04/05/2021 - 14:47

We are absolutely delighted to congratulate Professor Rebecca Kilner on being elected as a Fellow of the Royal Society. Becky is one of the leading lights working on the evolution of animal behaviour, and how behaviour then affects the pace and scope of subsequent evolutionary change. Using experimental evolution, her...

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Stone Age bear genome reconstructed from DNA in Mexican cave

Cam ac uk zoology department feed - Mon, 19/04/2021 - 17:30

A team of scientists led by Professor Eske Willerslev in the University of Cambridge’s Department of Zoology and the Lundbeck Foundation GeoGenetics Centre, University of Copenhagen, have recreated the genomes of animals, plants and bacteria from microscopic fragments of DNA found in the remote Chiquihuite Cave in Mexico.

The findings have been described as the ‘moon landings of genomics’, because researchers will no longer have to rely on finding and testing fossils to determine genetic ancestry and connections.

The results, published today in the journal Current Biology, are the first time environmental DNA has been sequenced from soil and sediment. They include the ancient DNA profile of a Stone Age American black bear taken from samples in the cave.

Working with highly fragmented DNA from soil samples means scientists no longer have to rely on DNA samples from bone or teeth for enough genetic material to recreate a profile of ancient DNA.

The samples included faeces and droplets of urine from an ancestor of the American black bear, which allowed the scientists to recreate the entire genetic code of two species of the animal: the Stone Age American black bear, and a short-faced bear called Arctodus simus that died out 12,000 years ago. 

Professor Willerslev said: “When an animal or a human urinates or defecates, cells from the organism are also excreted. We can detect the DNA fragments from these cells in the soil samples and have now used these to reconstruct genomes for the first time. We have shown that hair, urine and faeces all provide genetic material which, in the right conditions, can survive for much longer than 10,000 years.

“Analysis of DNA found in soil could have the potential to expand the narrative about everything from the evolution of species to developments in climate change – fossils will no longer be needed.”

Chiquihuite Cave is a high-altitude site, situated 2,750 metres above sea level. DNA of mice, black bears, rodents, bats, voles and kangaroo rats was also found. The scientists say that DNA fragments in sediment will now be able to be tested in many former Stone Age settlements around the world.

Professor Willerslev said: “Imagine the stories those traces could tell. It’s a little insane – but also fascinating – to think that, back in the Stone Age, these bears urinated and defecated in the Chiquihuite Cave and left us the traces we’re able to analyse today.”

Reference

Petersen, M.K. et al, Environmental genomics of Late Pleistocene black bears and giant short-faced bears. Current Biology, April 2021. DOI: 10.1016/j.cub.2021.04.027

Adapted from a press release by St John's College, Cambridge.

 

Scientists have reconstructed ancient DNA from soil for the first time, in an advance that will significantly enhance the study of animal, plant and microorganism evolution.

Analysis of DNA found in soil could have the potential to expand the narrative about everything from the evolution of species to developments in climate change – fossils will no longer be needed.Eske WillerslevDevlin A GandyAssistant Professor Mikkel Winther Pedersen with team members sampling the different cultural layers in the cave.


The text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified.  All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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StepWide - promoting the next generation of female researchers

News from this site - Mon, 19/04/2021 - 14:22

A new website created by 3 female postdocs shines a light on early career talent at the University of Cambridge and affiliated institutes. The StepWide website launched last month aims to support female, including trans women, postdoctoral researchers, from any discipline, to showcase their expertise and grow their online...

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Conservationists may be unintentionally spreading pathogens between threatened animal populations

Cam ac uk zoology department feed - Mon, 12/04/2021 - 10:00

The new report published in the journal Conservation Letters focuses on freshwater mussels, which the researchers have studied extensively, but is applicable to all species moved around for conservation purposes. 

Mussels play an important role in cleaning the water of many of the world’s rivers and lakes, but are one of the most threatened animal groups on Earth. There is growing interest in moving mussels to new locations to boost threatened populations, or so they can be used as ‘biological filters’ to improve water quality. 

A gonad-eating parasitic worm, Rhipidocotyle campanula, which can leave mussels completely sterile, was identified as a huge risk for captive breeding programmes where mussels from many isolated populations are brought together.  

“We need to be much more cautious about moving animals to new places for conservation purposes, because the costs may outweigh the benefits,” said Dr David Aldridge in the Department of Zoology at the University of Cambridge, senior author of the report.

He added: “We’ve seen that mixing different populations of mussels can allow widespread transmission of gonad-eating worms – it only takes one infected mussel to spread this parasite, which in extreme cases can lead to collapse of an entire population.”

Pathogens can easily be transferred between locations when mussels are moved. In extreme cases, the pathogens may cause a population of mussels to completely collapse. In other cases infections may not cause a problem unless they are present when other factors, such as lack of food or high temperatures, put a population under stress leading to a sudden outbreak.

The report recommends that species are only relocated when absolutely necessary and quarantine periods, tailored to stop transmission of the most likely pathogens being carried, are used. 

It identifies four key factors that determine the risk of spreading pathogens when relocating animals: proportion of infected animals in both source and recipient populations; density of the resulting population; host immunity; and the life-cycle of the pathogen. Pathogens that must infect multiple species to complete their life-cycle, like parasitic mites, will only persist if all of the species are present in a given location.

“Moving animals to a new location is often used to protect or supplement endangered populations. But we must consider the risk this will spread pathogens that we don’t understand very well at all, which could put these populations in even greater danger,” said Josh Brian, a PhD student in the Department of Zoology at the University of Cambridge and first author of the report.

Different populations of the same species may respond differently to infection with the same pathogen because of adaptations in their immune system. For example, a pack of endangered wolves moved to Yellowstone National Park died because the wolves had no immunity to parasites carried by the local canines.

The researchers say that stocking rivers with fish for anglers, and sourcing exotic plants for home gardens could also move around parasites or diseases. 

“Being aware of the risks of spreading diseases between populations is a vital first step towards making sure we avoid unintentional harm in future conservation work,” said Isobel Ollard, a PhD student in the Department of Zoology at the University of Cambridge, who was also involved in the study.

This research was funded by the Woolf Fisher Trust.

Reference
Brian, J.I., Ollard, I.S., & Aldridge, D.C. ‘Don’t move a mussel? Parasite and disease risk in conservation action.’ Conservation Letters, April 2021. DOI: 10.1111/conl.12799

Moving endangered species to new locations is often used as part of species conservation strategies, and can help to restore degraded ecosystems. But scientists say there is a high risk that these relocations are accidentally spreading diseases and parasites.

We’ve seen that mixing different populations of mussels can allow widespread transmission of gonad-eating worms.David Aldridge David AldridgeAt-risk species of river mussel


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