Bumblebees can tell each other apart using scent marks

We have discovered that bumblebees have the ability to use ‘smelly footprints’ to make the distinction between their own scent, the scent of a relative and the scent of a stranger.


beeBumblebees have the ability to use ‘smelly footprints’ to make the distinction between their own scent, the scent of a relative and the scent of a stranger. By using this ability, bees can improve their success at finding good sources of food and avoid flowers that have already been visited and mined of nutrients by recognising who has been there previously. A study conducted as part of Richard Pearce‘s PhD that shows this has been published in Scientific Reports today.

Bumblebees secrete a substance whenever they touch their feet to a surface, much like us leaving fingerprints on whatever we touch. Marks of this invisible substance can be detected by themselves and other bumblebees, and are referred to as scent marks.

We performed three separate experiments with bumblebees, where they were repeatedly exposed to rewarding and unrewarding flowers simultaneously that had footprints from different bees attached to them.

Each flower type either carried scent-marks from bumblebees of differing relatedness (either their own marks, sisters from their nest, or strangers from another nest), or were unmarked.

We discovered that bees were able to distinguish between these four different flower types, showing that not only can bees tell the marks of their own nest mates from strangers, but also that they can discriminate between the smell of their own footprints and those of their nest mate sisters.

This is the first time it has been shown that bumblebees can tell the difference between their scent and the scent of their family members. This ability could help them to remember which flowers they have visited recently.

Bumblebees are flexible learners and, as we have discovered, can detect whether or not it is they or a different bumblebee that has visited a flower recently. These impressive abilities allows them to be more clever in their search for food, which will help them to be more successful.

This work, published today in Scientific Reports, was funded by the EPSRC, through the Bristol Centre for Complexity Science. This blog posting is an edited version of the University of Bristol press release.

further reading

Pearce RF, Giuggioli L & Rands SA (2017). Bumblebees can discriminate between scent-marks deposited by conspecifics. Scientific Reports 7: 43872 | full text

Consensus trumps leadership and personality

sticklebacks‘Personality’ has been a big topic in behavioural ecology for well over a decade now, and work is still coming thick and fast showing that individual animals can show consistent sets of correlated behaviours in different situations, and that that different individuals can show different sets of these behaviours.  For example, many different species have been shown to have some individuals who are ‘bold’ risk-takers who are active in their response to stimuli, whilst other ‘shy’ individuals are less likely to take risks, and will be passive in their response.

However, when groups of individuals come together to behave in a social setting, it could be the case that these consistent personalities break down, as it may not be possible or suitable for every individual to follow their own personality-defined behaviour.  A recent paper in Science Advances from Christos Ioannou’s group (McDonald et al. 2016), that I was privileged to be involved with, demonstrates just this. The study looked at what happens when you put together groups of sticklebacks that have different personalities.

By testing the fish individually, we showed that there was consistency in how they emerged from a safe shelter and travelled through a ‘dangerous’ exposed area of water in order to reach a foraging site: some individuals were bolder than others.  However, when you put groups together with a range of bold and shy individuals, the shy individuals tended to lose their shyness and behave in a similar way to the bold individuals.  This effect is only temporary – once the fish became used to the test conditions and their groups, they reverted to their initial personality-defined behaviours.

This study suggests that personality isn’t necessarily consistent in individuals, and may well depend upon context. Being able to remain in a group is very likely to be important for sticklebacks, and it makes sense that shy individuals will mask their behaviour in order to maintain the protection of a group.  Whether this is ignoring the behaviour determined by their own personality, or rather another aspect of their personality that is defined by social context or some other aspect of state (see Dall et al. 2004 for discussion), it suggests that there is a lot more to be explored concerning how personalities are affected by groups.

further reading

Dall SRX, Houston AI & McNamara JM (2004). The behavioural ecology of personality: consistent individual differences from an adaptive perspective. Ecology Letters 7: 734-739 | abstract

McDonald ND, Rands SA, Hill F, Elder C & Ioannou CC (2016). Consensus and experience trump leadership, suppressing individual personality during social foraging. Science Advances 2: e1600892 | full text (open access) | pdf | blog posting from Christos Ioannou

“I don’t think I’ve ever seen a fat horse”

guest blog by Sarah Giles

photo copyright Sarah Giles 2014
photo © Sarah Giles 2014

The usual response to the mention of equine obesity is “I don’t think I’ve ever seen a fat horse”. Followed by a long-winded explanation by me of how horses don’t necessarily ‘look’ fat in the same way as we are used to recognizing fat humans. But they are. Our new study, published yesterday in PeerJ, showed that the prevalence of obesity in outdoor living horses and ponies was a staggering 27% at the end of winter, when we would expect outdoor living animals to be at their thinnest (!) and rising to 35% during the summer months, presumably due to all that lush, green, UK pasture.

So nearly a third of UK leisure horses and ponies could be clinically obese, and other previous studies have had similar findings. That’s a very similar level of obesity to that seen in the human population. In the same way as humans, horses may experience negative health consequences of obesity,  including metabolic conditions such as insulin resistance, but also a severe and debilitating hoof condition called laminitis which can render them chronically and even fatally lame.

The risk factors for obesity in any species are fairly straightforward, an energetic intake/exercise imbalance. Eat too much, do too little. But what makes some individuals more susceptible than others? Why do some horses seem to become obese when others do not under the same, outdoor living conditions? The study considered a wide range of food, exercise and management related factors, but by far the biggest risk factor was breed. Different horse breeds appear to have very different levels of obesity susceptibility. Our native UK breeds, including Welsh breeds, such as mountain ponies and cobs, as well as Dartmoor, Exmoor and New Forest ponies all appear to be at a much higher risk than  for example the Arabian type lightweight breeds.

It might be that native UK breeds, which have evolved to live on mountains and moorland, are just very efficient at storing fat reserves! They are designed to pile on the pounds during the summer months when food is plentiful, and use these extra stores to survive cold, harsh winters. The problem in domestic animals (which have changed very little physiologically from their wild counterparts) is that this harshness never really occurs in a domesticated environment and horses do not lose their fat reserves during the winter months. Instead they become incrementally fatter and fatter, year-on-year. The study showed that once horses and ponies become obese, natural seasonal fluctuation in body condition reduces and almost disappears. As a result, these animals remain obese, year-round.

The fact that supplementary food and exercise played such a small role in explaining obesity susceptibility in predominantly outdoor living animals is key here. There is clearly a lot of work to be done in investigating risk factors for obesity in these outdoor living animals. Could social and behavioural factors play a role? This is of real interest to us: keep your eyes on the blog for more details.

Further reading

Giles SL, Rands SA, Nicol CJ & Harris PA (2014). Obesity prevalence and associated risk factors in outdoor living domestic horses and ponies. PeerJ 2: e299 | full text | pdf