Lemming Population Cycles 100 years after Charles Elton

2024, the centenary of the publication of Charles Elton’s classic paper, Periodic fluctuations in the numbers of animals: their causes and effects, in Journal of Experimental Biology, also saw a flurry of interest on the same topic and the same mammals that occupied a large part of Elton’s review, lemmings.

Norway Lemming, Lemmus lemmus
Kevo Strict Nature Reserve, Finland, 2011
by Lakahillo (from Wikipedia)

The spectacular periodic fluctuations in lemming numbers—each cycle lasting 3-4 years—described by Elton from evidence gathered from around the Arctic have excited renewed interest because there had been suggestions that the large cyclical fluctuations in abundance are being wiped out by recent climate change, with consequences for the populations of predators and the whole ‘ecosystem’. However, twenty-four authors from Canada, France, Sweden, Finland, Norway, Russia, USA, Germany and Denmark analysed 24 sets of recent data gathered across the Arctic that recorded population changes over time.

This is the authors’ summary:

Reports of fading vole and lemming population cycles and persisting low populations in some parts of the Arctic have raised concerns about the spread of these fundamental changes to tundra food web dynamics. By compiling 24 unique time series of lemming population fluctuations across the circumpolar region, we show that virtually all populations displayed alternating periods of cyclic/non-cyclic fluctuations over the past four decades. Cyclic patterns were detected 55% of the time (n = 649 years pooled across sites) with a median periodicity of 3.7 years, and non-cyclic periods were not more frequent in recent years. Overall, there was an indication for a negative effect of warm spells occurring during the snow onset period of the preceding year on lemming abundance. However, winter duration or early winter climatic conditions did not differ on average between cyclic and non-cyclic periods. Analysis of the time series shows that there is presently no Arctic-wide collapse of lemming cycles, even though cycles have been sporadic at most sites during the last decades. Although non-stationary dynamics appears a common feature of lemming populations also in the past, continued warming in early winter may decrease the frequency of periodic irruptions with negative consequences for tundra ecosystems.

Two commentaries were published on the paper by Charles Krebs and by Rudy Boonstra, well-known ecologists who work on population changes. These commentaries highlight the fact that despite decades of research the underlying cause of these population cycles in lemmings and other rodents remains unknown. Similarly, the physiological processes involved are also unknown. I have written previously on Dennis Chitty’s (1912-2010) attempts to identify the cause of population cycles in voles (see here).

What is clear is that the mathematical modelling approach pioneered by Alfred Lotka in 1925 based on changes in numbers of predators and prey over time and which have been pursued actively ever since are, as is so often the case with mathematical models, inadequate. Experimental approaches to lemming and vole cycles have also not, in general, been successful, with other possible explanations of any changes observed and doubt whether the experimental conditions imposed are ones that actually obtain in the wild.

The importance of trying to understand what happens under the snow—the habitat of lemmings in winter where they feed and breed—was also stressed in the commentaries. Those observing lemmings only see the results of that activity when they count the population in spring and summer.

It is easy to forget when discussing the cause of cyclicity in population size and the changes in reproductive rate necessary to drive such changes that the the occurrence of ‘lemming years’ is a major wildlife phenomenon. Elton wrote of the Norway Lemming, Lemmus lemmus:

For many years the lemmings have periodically forced themselves upon public attention in Southern Norway by migrating down in swarms into the lowland in autumn, and in many cases marching with great speed and determination into the sea, in attempting to swim across which they perish. The details of the fate of the migrants do not concern us here and are fully described by [R] Collett [1911-1912]….Lemming-years in Norway have the status of great floods or terrible winters.

and of lemmings in northern Scandinavia:

It is obvious that the phenomenon of migration is far more striking than a mere increase in the numbers. The spectacle of processions of lemmings ecstatically throwing themselves over the ends of railway bridges, and falling to an apparently useless death below; the sea strewn with dead lemmings like leaves on the ground after a storm; lemmings making a bee-line across crowded traffic oblivious to danger; all these things are bound to make people talk.

Is was descriptions like this that gave rise to the popular notion generated and churned by the news media that lemmings commit suicide rather than simply die en masse when presumably moving in large numbers in search of food (Elton wrote not of food but of ‘relieving congestion in an area’). The Walt Disney film White Wilderness (1958) showed the sort of scenes described by Elton and others, with lemmings tumbling over the edge of a cliff. Decades after I saw the film at a meeting of the school natural history society in 1960 it emerged that captured lemmings had been pushed over the edge of artificial rockwork. The footage may have been fake and the lemmings poorly treated but film certainly conveyed what happens in the wild.

There are questions in my mind on this related phenomenon of migration, like the distances involved and whether they are acting like a plague of locusts, stripping one area of food before having to move on, given that their body size and increased activity would suggest they would  starve to death within a week without food. However, it is the response to  overcrowding view that dominated research in this area for decades. But that is another story.

To conclude, 100 years after Elton, the cause(s) and mechanism(s) of population cycles in lemmings—and voles etc—remain unsolved. But research activity and monitoring continues. We can only hope for progress.

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As an afternote I found reading Elton’s paper from 1924 well worth while. Not only did he consider mechanisms that may account for the phenomenon in lemmings but he also reviewed the occurrence of periodic booms in population of other rodents in some years. In the garden we had a large population of Bank Voles in the summers of 2018 and 2019, but not in the years before or since. Are the same or different mechanisms at play in different species is another abiding question.

Boonstra R. 2024. Population regulation and limitation—insights from lemming cycles: past, present and future. Proceedings of the Royal Society B 291: 20240660. doi.org/10.1098/rspb.2024.0660

Elton CS. 1924. Periodic fluctuations in the numbers of animals: their causes and effects. Journal of Experimental Biology 2, 119–163. doi.org/10.1242/jeb.2.1.119

Gauthier G, Ehrich D, Belke-Brea M, Domine F, Alisauskas R, Clark K, Ecke F, Eide NE, Framstad E, Frandsen J, Gilg O, Henttonen H, Hörnfeldt B, Kataev GD, Menyushina IE, Oksanen L, Oksanen T, Olofsson J, Samelius G, Sittler B, Smith PA, Sokolov AA, Sokolova NA, Schmidt NM. 2024. Taking the beat of the Arctic: are lemming population cycles changing due to winter climate? Proceedings of the Royal Society B 291: 20232361. doi.org/10.1098/rspb.2023.2361

Krebs CJ. 2024. Lemming population fluctuations around the Arctic. Proceedings of the Royal Society B 291: 20240399. doi: 10.1098/rspb.2024.0399

Central American Agouti. Honduras 2024

 

We saw the Central American Agouti (Dasyprocta punctata) several times while walking in the gardens of the Lodge at Pico Bonito in Honduras. These hystricomorph rodents are diurnal and live as mongamous pairs. Most times we saw one it was carrying one of these large seed pods.

Commander Hughes, bird artist, and his cousin, the ornithologist Pat Hall

After my article on the artist Commander Alfred Marcus Hughes appeared, Greg Davies commented:

Hughes also makes a cameo appearance in Beryl Patricia Hall's autobiography "A Hawk from a Handsaw" (1993). Hall was the doyenne of the British Museum Bird Room in the post-war III period, and a relative of Hughes.

On looking up Hughes and Hall I found that they were first cousins, once removed. Pat Hall was the grand-daughter of Hughes’s mother’s brother.

The comment also rang a bell in my neural circuitry. I was sure I could remember meeting Pat Hall but could not recall where and how. Then, looking her up to write this article, I found a photograph which provided all the answers. The date was 4 May 1972 when she received the Stamford Raffles Award at the AGM of the Zoological Society of London. I remember speaking to her briefly after the meeting when she seemed a bundle of nerves. For some strange reason on seeing the photograph I immediately remembered the coat she was wearing as being several sizes too big such that she and the coat seemed moved independently—a very weird thing to recall from the memory bank after 52 years.

Pat Hall receiving the Stamford Raffles Award from the President of the
Zoological Society of London, Prince Philip, Duke of Edinburgh.
4 May 1972
(Annual Report for 1972, ZSL)

Pat Hall was Beryl Patricia Hall (née Woodhouse). She was born to a wealthy family in Epson, Surrey, in 1917. She was thwarted by her parents in going to Cambridge to study maths and instead spent four years at home kicking her heels but also developing an interest in birdwatching. Thus in the 1939 Register, the emergency census, she is shown as employed on ‘domestic duties’ but also as involved in Air Raid Precautions work teaching ambulance drivers. She was determined to do something for the war effort and joined the Mechanised Transport Corps, a uniformed women’s civilian organisation that provided drivers to government departments and other civilian services.

After the outbreak of war Pat Hall became engaged to John Clavell Hall, in civilian life a Winchester-educated insurance clerk. He was commissioned into the Royal Artillery in March 1940 and posted to the Middle East. Pat volunteered to serve overseas driving ambulances. She was first in South Africa but was then moved to Egypt. The two were married on 21 May 1941 at Suez. However, this was no happily-ever-after story. By June 1943 John Hall had fought in Crete. was a temporary Captain and had been mentioned in despatches. However later that year he was captured during the Battle of Leros in the Dodecanese Campaign. Pat further developed her interest in birds in North Africa and ended the war in Italy still driving ambulances. After the war the marriage broke down and it was then that Hughes must have offered his help.

Alfred Hughes was a friend of the Norman Boyd Kinnear of the Natural History Museum. Kinnear, with no academic qualifications, had risen through the ranks of the museum world, beginning at the Bombay Natural History Society’s museum in Calcutta and continuing at the Natural History Museum in London. He had specialised in ornithology. By the time the war was ending he had been appointed Keeper of Zoology. In 1947 he was asked to take over as Director, past the normal retirement age, until a suitable candidate had been found in the post-war world. He stayed on as Director until 1950, sorting out the repair and restoration of the Museum needed after the disruption and damage caused by the War; for this he received a ‘K’.

Through that contact with Kinnear, Pat Hall was offered a post of Associate Scientific Worker in the Bird Room of the Museum. Ideally suited for those wealthy enough not needing to find paid employment, the scheme provided cheap and enthusiastic voluntary labour to the Museum. The position was paid at a rate—which did not change for ten years—of four shillings per hour, a wage which would have exceeded the average industrial pay in the 1940s. However, instead of that equating to a salary of around £800 per year, the maximum pay each year was capped at £100. Pat Hall was clearly keen to work at the Museum; she turned down a job offer from the BBC in order to work at the Museum.

James David Macdonald (1908-2002) was in charge of the Bird Room. He recognised her aptitude for the work she was doing and given her experience in Africa and her skills as a motor mechanic invited her, at her own expense, to be a member of a collecting expedition to south-west Africa that began in late 1949. The team, including Macdonald’s wife as the team doctor and cook, collected 1300 specimens of nearly 200 species during the six months in the field. After that for nearly 20 years Pat Hall divided her time between curatorial work, collecting expeditions and research based on the collections in the Museum. Her expeditions during the 1950s were to Africa. In 1953 she organised and largely funded a Natural History Museum-backed trip to what is now Botswana. Before and after an ornithological congress in Livingstone in what is now Zambia, she collected in Botswana and Angola respectively; overall she collected around 2000 specimens for the Museum. A short trip to north-western Botswana was her final experience of collecting in Africa.

Her publications during the 1950s and 60s were on African birds. Her largest was the outcome of eight years of work: An Atlas of Speciation in African Passerine Birds in 1970. Of 423 pages with 439 maps it was widely praised by reviewers. Herbert Friedmann (1900-1987) the American ornithologist who worked at the Smithsonian Institution wrote of its importance in The Auk of July 1971:

As Mrs. Hall states at the beginning of her introduction, this great series of maps constitutes the first attempt to show in graphic form, for the ready comprehension of the student, the results, "and the continuing process, of evolution in a large continental avifauna by means of plotting on one map the distribution of species believed to be immediately descended from a common ancestor." By placing closely related species on the same map it becomes evident where they overlap and where the are allopatric, and these facts give the field student indications of where to look and what to study in an attempt to assess and to interpret the past history of each of these current distributional patterns. It must be kept in mind, when using this atlas, that every existing specific distributional picture is not merely a discrete fact of local interest, but is always, and inevitably, the result of the past history of the species and of the region. This is the real, inherent interest in each of them, and each could become a valid point of departure for further study of the evolutionary vicissitudes of the particular species.

The Atlas had started as a joint effort with Reginald Ernest Moreau (1897–1970) the great amateur scientific ornithologist of his day. However, he became increasingly ill and the work fell on Mrs Hall. He died in the year of its publication.

Work on African birds was interrupted in the early 1960s. Macdonald heard of and then approached Harold Hall (no relation to Pat) an Australian philanthropist who was interested in supporting research. Harold Hall agreed to sponsor a series of five expeditions for the Natural History Museum (still labouring under the title of British Museum (Natural History)) around Australia. Macdonald was very keen to obtain more specimens for the Museum. The number of Australian specimens available within Britain had been depleted by the sale of Lord Rothschild’s collection (Rothschild was being blackmailed by a ‘titled lady’ and he needed the money) and another private collection to the USA.

Pat Hall led the third Harold Hall Expedition given her experience of collecting in arid parts of Africa. That was to the interior of Western and South Australia. She then edited the book describing the findings of all five expeditions which was published in 1974.

After the post-war recovery the Natural History Museum on its site in London was bursting at the seams with many thousands of specimens stored in unsuitable accommodation. In the mid-1960s, plans emerged to move the bird collection from South Kensington to the site of the Rothschild Museum at Tring in Hertfordshire. Pat Hall was opposed to the move on scientific grounds. It is easy to see why. She would also have had to move from Surrey to somewhere nearer Tring. She therefore decided to give up her work at the Museum in 1971. At the same time she moved from Epsom to the New Forest in Hampshire where it was noted she devoted her time ‘to friends, dogs, horses and village life’. However, retirement from the ornithological world in which she was well known came more gradually. She was in demand as an editor, speaker and organiser. What appears to have been her last job was presidency of the 4th Pan-African Ornithological Congress in 1976. That caused her particular hassles because of its move at the last minute from Kenya to the Seychelles over political problems.

It was said that the award which gave her particular pleasure was the Stamford Raffles Award of the Zoological Society of London for 1971—presented by the Society’s President, Prince Philip, Duke of Edinburgh at the Annual General Meeting I attended in 1972. This is how the Annual Report recorded it:

The Stamford Raffles Award (awarded to an amateur zoologist for distinguished contributions to zoology) to Mrs B. P. Hall, British Museum (Natural History), in recognition of her work on the taxonomy and zoogeography of birds, particularly those of Africa. The award was a sculpture in bronze, Wild Boar, by Miss Elisabeth Frink.

It was though the final paragraph of citation for the Union Medal of the British Ornithologists’ Union that best sums up what she had achieved:

Her scientific work has already been widely recognised, by her election as Corresponding Fellow of the American Ornithologists' Union, and by the awards of the Gill Memorial Medal of the South African Ornithological Society and the Stamford Raffles Award of the Zoological Society of London. It is most fitting that the Union Medal should now be awarded to Pat Hall, who has so strikingly shown that the heights  of ornithological achievement can still be scaled without the benefit of formal academic qualifications and institutional backing.

Retirement saw her adding two books to the one she had written with Derek Goodwin in 1969, a book published privately of nonsense verse about their lives in the Museum, Bird Room Ballads; Alfred Hughes provided the illustrations. The next was the story of her life in the Mechanised Transport Corps, What a Way to Win a War (1978, Midas Books, Tunbridge Wells). Finally, in 1993 came A Hawk from a Handsaw (1993, privately published). I have not been able to find a copy of the latter but her obituarist for The Ibis noted that it gave her side of what proved to be an unhappy collecting trip to Angola.

I wonder if Alfred Hughes realised that in speaking to his friend Kinnear he was launching his cousin Pat Hall on a pathway to her becoming a major player in classical ornithology of the 20th century. The Hughes-Hall family axis runs wide and deep in the ornithology of Africa and Asia.

Beryl Patricia Hall died on 4 August 2010 in a nursing home at Fishbourne, Hampshire.

Prys-Jones R. 2011. Beryl Patricia Hall (née Woodhouse), 1917-2010. Ibis 153, 913-914.

An American Crocodile: Honduras 2024

Last month we saw this American Crocodile (Crocodylus acutus) in the lower reaches of the Rio Cuero, Honduras, just about in the centre of its geographical range.

The American Crocodile prefers the somewhat saline waters of estuaries and mangroves and in this respect resembles the Estuarine or Saltwater Crocodile (C. porosus) of south-east Asia and northern Australia, a story I will return to in my Salt Glands Revisited series. It is also one of the largest species of crocodilian.

Basking with the mouth open—and thereby showing their very impressive set of teeth—appears to be concerned mainly with thermoregulation. Under the sun the head warms more quickly than the bulky body. Evaporative cooling from the tissues lining the mouth will lower the temperature of venous blood leaving the head. Provided there is a countercurrent arrangement whereby arterial blood entering the head is cooled by the venous blood passing in the opposite direction the brain will be kept relatively cool while the rest of the body gets to the optimum temperature. That’s the standard story but I have not checked whether or not there has been any experimental demonstration of the cooling in action. The reason I wonder, is that if, during basking, the blood from the body is relatively cool why the high rate of blood flow to the brain does not also keep the brain cool without the need for evaporative cooling? Or does the head get so hot that cooler blood from the body is insufficient to prevent the brain from suffering heat damage? Somebody who knows a lot more about crocodiles and their thermal physiology will put me right.

We asked if the crocodiles were dangerous to the human population especially the children. We were told not. Salties or Nile Crocodiles they are not.

George Cuvier in 1807 was the first to describe the American Crocodile but considered it another species of alligator. It took another Frenchman, the brilliant but mercurial Constantine Samuel Rafinesque, then working in the USA, to suggest in 1822 that it was not alligator but a crocodile.

Crocodylus acutus Distribution
Achim Raschka
BB BY-SA 3.0 Wikimedia Commons

Dear Sam, Sorry to hear you died in 1956. The crassness of modern ‘tech’

The crassness of modern life is sometimes exemplified by the ‘tech’ companies that make their business the distribution of scientific papers from the past and present and an attempt to be the site of discussion between scientists.

I was sent a link by one of their regular and too frequent emails drawing my attention to a paper by Samuel Brody (with Arthur Chester Ragsdale, 1890-1969, and Charles Wesley Turner, 1897-1975). The last time I actually read that paper was as an old-fashioned pre-Xerox photocopy made in the 1950s in the collection of a late colleague. How nice to read it again and within milliseconds it was downloaded. But then came a the follow-up seconds later inviting me to thank the author and to tell him what had sparked my interest in the paper. There was though a problem. The author had died in 1956 so where was the message to be sent? The same place as emails to Santa Claus?

It is difficult to appreciate the mindset of those who think the science they are interested in began within the last ten years. Especially that is when they are encouraged to think so by PhD supervisors, as, regrettably, is the case even in UK here we once had a more rigorous respect for knowing the literature.

So I shall not be writing to thank Sam Brody but it is worth pointing out who he was and why the research he did is still important.

Sam Brody ca 1930 when he was a
Guggenheim Fellow in 1929 and 1931
From here

Sam Brody produced the famous mouse-to-elephant curve which shows how metabolic rate varies with body weight and which followed up Max Kleiber’s work on a few species which suggested that metabolic rate (effectively oxygen consumption) did not increase linearly with body eight but as around the three-quarter power of body weight. In other words metabolic rate per kilogram is much lower in the elephant than it is in the mouse. The reason for this relation between metabolic rate and body weight is still a very active interest although it does seem that a present more heat has been generated than light has been shed on the problem in recent years.

A second area of research in which Sam Brody is remembered is for his demonstration that the frequency of milking in dairy animals leads to an increase in the rate of milks secretion. The mechanism by which that happens kept me occupied for many years and has particular application in not only dairy animals but also in human lactation where the frequency and completeness of milk removal are key determinants of breastfeeding success.

Samuel Brody was professor of dairy husbandry in the University of Missouri. He was born in Lithuania in 1890. He emigrated to Canada in 1906 where he worked as a machinist, miner, fisherman and door-to-door salesman. He then obtained a place across the border as a student at the National Agricultural School in Pennsylvania. Hearing of great things happening at the University of California at Berkeley he had to teach himself to read and write in English in order to pass the entrance exam and study there. He graduated in 1917 in biochemistry. Following a masters he spent a short time in the US Air Force and worked in the University of California until he appointed to his post in Missouri in 1920. He died in his office in August 1956.

Brody’s work on growth, metabolism, thyroid function and milk production established his international reputation—which leads me on to my second point. It is little recognised that advances in human reproductive physiology in particular and in human health generally have been made under the aegis of funding for agricultural research. With that funding drastically reduced in recent decades, particularly in UK, that generation of new knowledge has ceased—yet another reason for condemning successive governments and devolved administrations for following the mantra of its unimportance with agriculture only being responsible for 2% of GDP but ignoring the rather important matter of national food security and its 100% role in keeping people alive.

Meanwhile the crassness continues. In requesting that I ask co-authors to join, a list is provided of those not belonging. That list includes one who has been dead for 49 years.