Dr Hannah Rowland

Tel: +44 (0) 1223 331 759
Fax: +44 (0) 1223 336 676
Email: hr325 at cam.ac.uk

Position held: Junior Research Fellow, Churchill College

Personal website: hannahrowland.co.uk

Bitter taste perception
Many plants and animals contain toxic chemicals in order to deter predators. For example plants defend themselves with a variety of compounds such as nicotine, caffeine, and cyanides, which are harmful to the animals that eat them. Many toxins found in potential foods are perceived as bitter tasting, thereby helping animals to discriminate edible from dangerous foods. Bitterness perception occurs when chemicals reach taste receptor cells on the tongue and interact with specific bitter-taste receptors. A sense of taste helps animals decide whether a food should be consumed or rejected.

My research explores how non-mammalian vertebrates recognize, perceive and respond to bitter tastes.

Many species of plants or animals have evolved striking resemblances to inanimate objects found in the same locality, and are described as masqueraders. Species from taxa as diverse as insects, fish, amphibians, reptiles and birds are thought to employ masquerade for both protective and aggressive purposes.

For example, stick insects look remarkably like the twigs of the branches on which they sit. The Biston betularia caterpillar in the image below is virtually indistinguishable from an oak twig (in case you can't tell, the caterpillar on the one on the bottom!).

The comma butterfly Polygonia c-album (when sitting with its wings closed) and the Amazon fish Monocirrhus polycanthus are almost indistinguishable from leaves; plants from the genus Lithops are easily mistaken for stones; the spider Ornithoscatoides decipiens closely resembles bird-droppings, and the leafy sea dragon Phyllopteryx eques is often misidentified as sea weed. Such species are thought to benefit from their visual appearance by causing predators or prey to misidentify them as the object that they mimic, resulting in protection from predation or increased access to prey.

The diversity of signals employed by animals has attracted the interest of scientists and philosophers for centuries, dating back as far as Aristotle, who first recognised that an octopus could change its colour so as to look like its adjacent stones. My thesis explored the visual and behavioural ecology of countershading in lepidopteran larvae; in which animals display darker pigmentation on those surfaces exposed to the most lighting. When a uniformly coloured cylinder is illuminated from above by the sun, its upper surfaces become more brightly illuminated than the underside, which lightens the tone of the upper parts, and darkens the underside. Such shading allows us to perceive surface shape, and is hypothesised to aid visually hunting predators, like birds, in finding prey. For animals such as caterpillars, which live among flat leaves, this poses a great problem for concealment from predators.

It was artist and naturalist Abbot Thayer, who hypothesised a mechanism by which lepidopteran larvae might reduce their visibility to predators. The commonly exhibited gradation of pigment on the body of an animal, he proposed, would counterbalance such conspicuous shadows cast on the underside of an animal, which would reduce the visual information such as depth and projection to visually hunting predators The theory of camouflage by countershading has been much debated in recent times, and so my thesis set out to determine whether the presence of a graded colouration was a better form of camouflage than plain matching of the background.

I reared a selection of countershaded and non-countershaded lepidopteran larvae, including: eyed hawkmoth, elephant hawkmoth, poplar hawkmoth, puss moth, orange tip, large white, small white, clouded drab, and hebrew character. By measuring the colour of the larvae, I designed artificial prey which matched the visual characteristics of real animals. I then presented these artificial larvae to bird predators, to determine if countershading made them more difficult to find. I found that countershaded prey were indeed harder to detect by garden birds, than simple plain coloured prey. In conclusion, I used both field and lab studies to show that the very common pattern of colouration, known as countershading, has evolved to reduce the detectability of animals like lepidopteran larvae to their main type of predators.

Academic History
I finished my PhD, entitled ‘The visual and behavioural ecology of countershading and other defences’, in November 2007 under the supervision of Mike Speed. My thesis explored the evolutionary ecology of signaling systems, studying both predator behaviour and prey defences. I studied wild free-living birds in the field, and captive wild caught birds in aviary based experiments - the ‘Novel world’ system at the University of Jyvaskyla. I had four papers published from my thesis, with one in Nature (Rowland et al., 2007 ). My thesis was awarded two prizes, the Thomas Henry Huxley award from the Zoological Society of London (For best Zoology thesis in UK), and the Royal Entomological Society Wallace award (for best Entomology thesis in World).

I remained at Liverpool for my first postdoc, where I investigated the role of wild and domestic bird feeding decisions on the alternative causal mechanisms by which mimicry of warning signals may have evolved. Findings from my studies have been published in Science, PNAS, Behavioural Ecology, and Ecology Letters.

I recently completed a NERC-funded postdoctoral research associate at the University of Glasgow, where I investigated the evolution of masquerade, in which prey mimic the visual appearance of inanimate objects such as twigs and leaves.

Scholarships and Awards

International and national awards
Thomas Henry Huxley award and Marsh prize 2008 Presented for the best zoological doctoral thesis produced in Great Britain or Northern Ireland
The Alfred Russel Wallace award 2008 For post-graduates who have been awarded a PhD, whose work is considered by their Head of Department to be outstanding. The research involved should be a major contribution to the Science of Entomology.
Applied Vision Association Richard Eagle award 2007

Grants and scholarships
John Lennon Memorial Scholarship 2005/2006
British Trust of Ornithology Trainee ringing grant 2005
Liverpool Biological Society 2nd Prize 2003
Gossage University Undergraduate Scholarship 2002

Research grants awarded
2011-2012
British Ecological Society early career grant: the ecological and energetic factors underlying variation in dietary plasticity in both resident and migratory bird species. Integrating behaviour, physiology and genetics to develop specific recommendations for effective conservation. £9K
ASAB research grant: hormonal signals in predator-prey interactions: A predator’s perspective £5K

2010-2011
Wingate foundation research fellowship: the evolution and function of bitter taste in birds £7.2K

2008-2011
NERC research grant: Masquerade: critical testing of the ecology of disguise. (researcher co-investigator)

• Rowland, H. M., Mappes, J., Ruxton, G. D., & Speed, M. P. (2010). Mimicry between unequally defended prey can be parasitic: Evidence for Quasi-Batesian mimicry. Ecology Letters, 13, 1494- 1502.
• Rowland, H. M., Wiley, E., Ruxton, G. D., Mappes, J. M., & Speed, M. P. When more is less: the fitness consequences of predators attacking more unpalatable prey when more are presented. Biology Letters, 6(6), 732-735.
• Rowland, H. M., Hoogesteger, T., speed, M. P., Ruxton, G. D., Mappes, J. M. (2010). A tale of 2 signals: Mimicry between aposematic species enhances predator avoidance learning. Behavioral Ecology, 21(4), 851-860.
• Rowland, H. M. (2009). From Abbott Thayer to the present day: what have we learned about the function of countershading? Philosophical Transactions of the Royal Society - B, 364, 59-527.
• Rowland, H. M., Cuthill, I. C., Harvey, I. F., Speed, M. P., & Ruxton, G. D. (2008). Can't tell the caterpillars from the trees: countershading enhances survival in a woodland. Proceedings of the Royal Society of London - B, 275(1651), 2539– 2545.
• Rowland, H. M., Speed, M. P., Ruxton, G. D., Edmunds, M., Stevens, M., & Harvey, I. F. (2007). Countershading enhances cryptic protection: an experiment with wild birds and artificial prey. Animal Behaviour, 74, 1249-1258.
• Rowland, H. M., Ihalainen, E., Lindstrom, L., Mappes, J., & Speed, M. P. (2007). Co-mimics have a mutualistic relationship despite unequal defences. Nature, 448, 64-67.