“A friend (Jerome Harding) and I decided to escape from the urban Chicago and made a trip around the tip of Lake Michigan to the Indiana Dunes one weekend morning. We were walking along the lakeshore, we noticed the abundance of insects among the debris above the water line. It suddenly occurred to me that we were looking at a Bumpus [1899]-like sampling situation. I quickly showed Jerome, a computer programmer, how to capture and save two samples of the most abundant insect, the pentatomid bug.”

“Although Darwin first suggested that the peacock’s train had evolved as a result of female choice, no one had tested this idea. I was working at Whipsnade Park on a study of Chinese water deer, and, whilst staying overnight in the park, noticed the free-ranging peacocks displaying in groups (lekking). I thought that it would be feasible to study the peacocks at Whipsnade (that it would be relatively easy to catch and mark them) and test Darwin’s hypothesis.”

“As an undergraduate, I had spent a month in the Amazon, right near where I ended up working, and that really inspired me to think about the diversity in those forests and to try to make sense of the hyperdiversity that is found in places like the Ecuadorian Amazon.”

“As I completed my PhD work, I became increasingly interested in fieldwork and functional explanations of behavior that put me on a track to evolutionary biology. When I interviewed for an assistant professorship at the University of California at Santa Cruz, I was asked if I would be interested in studying the seal colony at Año Nuevo, about 30 km up the coast. I answered yes, knowing next to nothing about seals. When I visited the colony in December 1967, I was captivated. I asked questions that could not be answered. Males were fighting in the middle of a large group of females. It seemed like a dominance hierarchy as had been observed and reported in barnyard chickens. But dominance hierarchies were not considered important at the time because most studies were in the laboratory and males were forced to fight to produce a winner. The hierarchy was contrived. But it was obvious on first sight that the male elephant seals I observed exhibited something like a dominance hierarchy. But one had to mark the males to really tell what was going on. I immediately wrote a research proposal on male-male competition. It was funded and I started doing fieldwork on elephant seals. This was the beginning of a long-term project that lasted 40 years (it is still going under the direction of others; I am retired).”

“Blue jays are difficult to work with in the laboratory because they’re very wired. They’re very intense. If you catch them as adults, they never tame, they never relax in captivity. They will beat themselves up on the wires. So what we have done – this is the way Al Kamil developed it years ago — was that you find a blue jay nest and you go and watch it for the point at which the young hatch, and you look for the moment at which the nestling’s eyes are just opening. It’s about 10 days after they hatch. At that point, you take the babies out of the nest, bring them to the lab and then you hand-feed them. Essentially, they associate people with food for the rest of their lives. But they never get pleasant about it. They don’t like you and they will bite you on a regular basis, but they do behave properly in the apparatus. So, they were locally caught here in Lincoln. Some of the best places are nests in people’s backyards, or there are several parks and graveyards. Cemeteries are very good for blue jays and we’ve picked a number of them from there.”

“But then when I was down there tromping around looking at all these species in their respective habitats, I was so struck by how many oaks there were. When I came back from that initial inquiry trip, just trying to scope out field sites, it struck me that it really might be more interesting to focus on the oak clade and look at the evolutionary history of how different lifespans evolved within that.”

“During a visit to East Africa in 1975, I saw long-tailed and Jackson’s widowbirds on their savanna breeding grounds in the Kenyan highlands. Why were male long-tailed widowbirds, with their black plumage, red wing epaulet and, especially, a half meter long unwieldy tail, so different from the females [...]?”

“Editors these days might not let me get away with such a chatty style. But I enjoy reading papers where you feel you are out there with the researcher, watching the animal and eavesdropping on the study. These days, of course, statistical analysis and quantification and use of computers has changed the way we do research for the better. There is absolutely no question about that. But I do think that people quite often get beguiled by numbers and statistics and lose track of the natural history, which I think should always be the starting point. I think observation from natural history is the most interesting thing and if you then can combine that with statistics and modelling then that’s great. But complicated statistics and numbers for the sake of it just makes the whole study dull.”

“First of all, I observed there were helpers at the nest. And at that time I did not have the book so I was surprised to see adult birds that were sexually mature that did not reproduce themselves but helped other birds raising their offspring and incubating the egg. And then I also found out that the whole island was covered with territories. There was no empty space left on the island for other birds to establish new territory. So I thought maybe habitat saturation was a driver for cooperation. And then I mentioned this to a lecturer I knew in Holland. And he said, oh, you should read that book by Krebs and Davies. It was one of my old lecturers, and then he sent a copy of the chapter on cooperative breeding of that book to me (it took 3-4 weeks for the post to get it to me). I read that chapter and I realized that cooperation sort of has been observed in other bird species and mammalian species. However, I did observe other things which were not written in the book chapter. But at least, the book chapter formed the basis for my thinking.”

“I did have a look at the paper again recently, in response to your questions, and it does seem like something from a different era, where natural history and simple field observations were considered to be important. Times have changed enormously in academia, and it is now extremely difficult to obtain money to do this sort of work. This is a shame, to say the least, as there is so much that we don’t know about the natural world.”

“I had this idea about fruit dispersal and group foraging in a little bat that both feeds on nectar and fruit. But these bats were very hard to study because they were very easily disturbed and would fly out of the roost whenever I tried to catch them. Vampire bats, on the other hand, were really common and very easy to work on. Around the same period of time – those three months – Jack Bradbury went to a regular bat meeting where he heard a German biologist – Uwe Schmidt – report that he saw vampire bats regurgitate blood to each other in his captive colony. Jack wrote me a letter and told me about that observation and said that, maybe, this might be something I wanted to think about. And so I actually began, at that time, trying to catch and band vampire bats, and then dreamed up the project that I subsequently did between ’78 and ’83.”

“I searched the literature for some species to work on for my PhD thesis. I wanted to look at how variation in calls influenced mate preference within the species, and I decided to work on red-eyed tree frogs in Panama. But they were very high up in the canopy and I was having a difficult time recording the males and a difficult time watching the matings. And when I was trying to record these males, all these Tungara frogs would be calling at my feet. They were very common and I would always be kicking the frogs to shut them out so I could hear the red-eyed tree frogs calling. That’s when I thought that since these Tungara frogs are always calling, maybe I should study them instead. That’s how I started to study them.”

“I spent the whole time – every day, all day – watching butterflies. I almost never went into town, except to get shopping at the end of the day. I would just wander around with a net and a notebook and a stopwatch. That’s all I used. The first thing I did was to mark a lot of individuals so they could be recognised. I remember being delighted how easy this was compared to trying to catch pied wagtails. I would see a butterfly in a sunny spot, capture it in a net and mark it with felt tip pen through the net. I didn’t actually have to handle the butterfly at all. This way I marked several hundred during the study. On my first day I decided to watch one individual for the whole day, just to try and get a feel for what it was like to be a speckled wood butterfly. I watched one male for six hours or so, in one little sunny patch. As the sun moved across the sky, the sunny patch moved over the woodland floor, and the male followed it faithfully, travelling something like 20 or 30 metres during the day, always staying in his little sunny spot. I noticed that he didn’t spend any time feeding there. He just perched and whenever anything came close by he would sally out and inspect it. Often it was another insect, perhaps a ladybird or another species of butterfly, and he’d then very quickly ignore it and return to his perch. But if it was another speckled wood butterfly he was very interested. If it was a male, they would have a brief spiral flight, and then one of them would retreat. It was always the owner who would come back to the territory. If it was a female he would follow and court her, but almost always she said no. She would fold her wings and depart, and he would then leave her alone. Subsequently, I discovered that these females which said ‘No’, were already mated and laying eggs. In butterflies, females can say ‘No’ and that is the end of it. There is nothing the male can do. But occasionally, a female would say ‘Yes’ and the male would then leave the territory and fly up and mate with her up in the canopy. These simple observations suggested to me that what the male was doing in these sunny spots was looking out for females. The next question I asked was whether these little chase, these little spiral flights, were territory defence. You might think, well it is obvious they must be! But there was some controversy back in the 60s and 70s about whether butterflies really did defend territories or whether these little interactions were simply a case of butterflies spacing out amongst the available habitat. So I thought it was very important to test whether these other intruding butterflies really wanted to settle in the territories. So I removed the original owners, kept them in a net, and when one of these butterflies from the canopy came down I saw what they did. I discovered that in all cases where I had removed an owner, the new comer settled in the territory and began to defend it. And that suggested to me that these spiral flights had previously kept them out, so it really was territory defence. I was very pleased with that very simple removal experiment; these other butterflies were clearly keen to get the territories when the vacancy arose.”

“I started to work on fruits and frugivores in the Sierra de Cazorla area in the fall of 1978. In 1981, I had, for the first time, the opportunity to witness a massive spring flowering, and then an autumn fruiting event, by Phillyrea latifolia. I was absolutely amazed by the spectacular phenomenon, as all trees were in flower, and later in fruit, over countless hectares. By then I was well aware of the concept of ‘mast fruiting’ as applied to dry-fruited plants like oak or beech, but had not heard about any similar instance for fleshy-fruited plants. In principle, satiation of mutualists did not seem to me a reasonable strategy for a fruiting plant, which spurred my curiosity. In the years following 1981, I kept waiting patiently for another massive flowering event to take place, so that a study on the seed dispersal consequences of massive fruiting could be planned and undertaken. That finally happened in 1989, and we went ahead with our study that year.”

“I think that ours is certainly not the full explanation; I don’t think it is the full story. I find it hard to believe that if a bee flies, for example, distances greater than 10 kilometres in search of food, it relies purely on optic flow. It must feel tired, it must feel exhausted, its crop would be almost empty, and it would feel a sense of fatigue – all these would also indicate distance in some way, I think. Maybe for short to medium flights, optic flow is the only cue, but for longer flights I think other cues will be required.”

“I wasn’t a birdwatcher from a young age. However, I did spend a lot of time in the mountains and in conifer forests when I was young. My passion for birds started in college. Then in the summer before starting my PhD, I helped a friend with his PhD, and crossbills were quite common in that forest. I got to know them a little bit more. So, I had some feel for crossbills and their habitats, and knew enough to believe they could be interesting to study.”

“I worked in Tanzania and Uganda during my thesis on Colobus monkeys. And, while they were very interesting, the problem was that they live in the canopy, between 70 and 120 feet above your head. Your capacity to recognize individuals is quite limited. Your capacity to collect biological material from them is quite limited. Your capacity to measure food availability is quite limited. And having spent three years working on this, for my next project, I wanted both to be placed in the UK rather than overseas, and I wanted a more tractable species where one could actually get access to the animals, where one could ideally collect biological material for individuals, where you could measure the food supply, and where you could follow the survival of individuals throughout their life. And that immediately made me realize that really one wanted a terrestrial species, and you wanted a terrestrial species that was visible and lived in a habitat where you could actually see what was going on. And red deer in Scotland live in open environments. I’d had experienced them previously when I worked for Roger Short taking a film of his work on the reproductive physiology of red deer. So, I knew about it. And red deer are one of the principal grazing species throughout much of the highlands of Scotland, so there’s an economic interest in them. And all of those made me realize the red deer were a good animal to work on.”

“It was almost evening when the adult male langur I called “Mug”, who had been stalking this mother-infant pair for some days, caught hold of her infant and was running with him in his jaws along the rooftop of the Phiroze School, as two older females in the group (“Sol” and “Pawless”) rushed at him to try and retrieve his victim. Years later, the self-sacrificing bravery of these old females at or near the end of their reproductive careers would play an important role in the development of my thinking about the roles group members other than mothers played in human evolution”

“Most of my ideas come from just birdwatching. Wicken Fen, just a short cycle ride from Cambridge, has a good population of common cuckoos, which parasitize reed warblers. Ever since I was an undergraduate here, I have been astonished by the sight of a little reed warbler feeding an enormous cuckoo chick; why are they fooled by a chick that’s seven times their own body mass? Steve Rothstein’s papers on cowbirds in North America had shown how one could do experimental work on host defences using model eggs. And it occurred to me we could do exactly the same to try and work out whether reed warblers have defenses simply by playing the part of the cuckoo ourselves and parasitizing nests with model eggs. So, it was this mixture of bird watching and reading Steve Rothstein’s studies which inspired me. There was also a wonderful paper by Richard Dawkins and John Krebs on arms races in nature pointing out that a lot of biodiversity evolves in response to interspecific interactions. That also bubbled around at the back of my mind as a theoretical boost to this study. But it was pure natural history interest which really drove the choice of the reed warbler and the cuckoo. We just thought it’d be fun to go around Wicken Fen pretending to be cuckoos!”

“One challenge to working with primates is that you only have a limited amount of time that you can work with them each day. They need to eat, rest, and socialize, there are husbandry needs, and there are usually several people working with them who are sharing time. In a typical morning, we’d come in and feed them first. The monkeys lived in a large social group in large indoor-outdoor enclosures [...], so we’d call them inside and offer whoever we were working with the opportunity to come into the testing chamber, which is attached to the indoor area in their home enclosure. They only participate if they choose to, so if they came in, we’d run the study and then let them back outside to join the rest of their group.”