Author: Richard Oldham

It’s a colorful world – let’s keep it that way.

In many animals, the eyes have developed to be able to discriminate different colors and levels of brightness to gain an efficient way of obtaining accurate information about their biotic and abiotic environments. Animals use visual cues (e.g. color patterns, movement detection, etc.) to find appropriate mates, to find food, or to avoid predation. The study of how visual systems evolve and function to meet the ecological needs of animals is known as visual ecology (Cronin et al., 2014). Coloration is extremely important for the discretion of species, along with determining characteristics about the other organisms, like fitness.

For example, a female cardinal evaluating a male in sunlight needs to discriminate the cardinal male from other species, and the green background foliage to evaluate the color and quality of his plumage using color vision (Cronin et al., 2014). Ornamental traits are understood to be reliable indicators of an individual’s condition (Zahavi, 1975). In birds, females choose brightly colored males because it can help determine if offspring will have heritable characteristics which may help future generations survive (Hamilton & Zuk, 1982). But can humans alter this coloration through societal activities? Perhaps by altering the environment, coloration can also be altered.

One way humans can alter the environment is through the introduction of chemicals. Chemical pollution can have negative effects on the development, physiology, behavior, reproductive success, and survival of wildlife (Lifshitz & St Clair, 2016). The expression (or lack of expression) of bright ornamental traits reveal an honest indicator of an organisms encountered environmental stress, such as living in human-induced pollutants.

An extensive review by Lifshitz & St. Clair (2016) puts together how chemical pollution can alter the ornamentation of animals. Many of these chemicals reduce the carotenoid (orange and red) and increase the melanin (brown and black) pigmentation found in wildlife. For example in birds, male red-legged partridges (Alectoris rufa) exposed to the herbicide Diquat increases the area of black plumage, and reduces the red coloration of their beaks and eye rings. Thiram fungicides and imidacloprid insecticides also reduces the red coloration of A. rufa’s eye rings.

A. rufa

Aroclor (a PCB) reduces the carotenoids in the facial skin of male American kestrels (Falco sparverius).

F. sparverius

Additionally, metals like lead, cadmium, zinc, and copper increased the area of black breast stripes while lowering the carotenoid coloration of breast feathers in great tits (Parus major).

 

P. major

 

Monitoring the coloration of animals has enormous potential to be a non-invasive tool for detecting subtle and early effects of pollution long before they can be seen as population level effects. Species which exhibit carotenoid-based ornamentation can be particularly promising as a highly responsive indicator of pollution (Lifshitz and St. Clair, 2016). The adoption of regulations informed by coloration and sensory ecology is needed to mitigate the effects of human-induced environmental change and is vital for behavioral ecology and conservation (Lifshitz and St. Clair, 2016; Lim et al., 2008).

References

Cronin TW, Johnsen S, Marshall NJ, Warrant EJ (2014). Visual ecology. Princeton University Press.

Hamilton WD, Zuk M (1982) Heritable true fitness and bright birds: a role for parasites? Science 218: 384–387.

Lifshitz N, St. Clair CC (2016). Coloured ornamental traits could be effective and non-invasive indicators

of pollution exposure for wildlife. Conserv Physiol 4

Lim MLM, Sodhi NS, Endler JA (2008). Conservation with sense. Science 319:281-281.

Zahavi A (1975) Mate selection—a selection for a handicap. J Theor Biol 53: 205–214.

 

Photo credits

Cardinal diagram – Cronin TW, Johnsen S, Marshall NJ, Warrant EJ, 2014. Visual ecology. Princeton University Press.

 A. rufa – https://www.juzaphoto.com/life.php?l=en&s=alectoris_rufa

F. sparverius – https://commons.wikimedia.org/wiki/File:Falco_sparverius_-Oregon_Zoo,_Portland,_Oregon,_USA_-male-8a.jpg

P. major – http://www.flickriver.com/photos/diniscortes/sets/72157604962242130/

 

What’s all that noise about?

Audition and the processing of acoustic information through hearing is critically important for animals to express territory, find suitable mates, alert others of predators, and much more. Auditory communication is found in many animals via vocalization. Some well-known examples of animals which use auditory communication are: songbirds, bats, whales, crickets, and frogs; however, auditory communication can occur in species which you may have never thought of- like fish! Recently, off the coast of Port Hedland in Western Australia, scientists have found evidence that fish actually sing together in a chorus at dawn and dusk (Parsons et al., 2016). These fish choruses occurred predominantly between late spring and early autumn.

 

Communication is a two-way street – both producing and hearing sound being important. So what happens when humans introduce noise into an animals’ environment? What would you do if you are trying to communicate with another person in a noisy bar? Perhaps you would talk louder, shift your voice higher, repeat yourself more often and use less complex sentences, or maybe just leave the area. Other animals may exhibit similar behaviors- birds in a noisy environment will also vocalize louder (Brumm, 2004), shift their vocalizations to higher frequencies (Slabbekoorn & Ripmeester, 2008), increase vocal redundancy (Brumm & Slater, 2006), or just avoid the area during times of high noise (Bergen and Abs, 1997).

Noisy environments are associated with increased urbanization. Noise can be introduced through things like: aircrafts flying overhead, automobiles driving down a busy street, the construction or renovation of buildings, neighbors mowing their lawn, ect. Urbanization is increasing globally at a rapid rate, with few places escaping human-induced changes. As a result, urbanization has become a major driver in ecology. One thing we can all agree on is that sometimes being in a noisy environment can be stressful, especially if you are trying to be productive. But how does stress, induced via noise, affect wild animals?

Chronic stress has been linked to important processes, such as the reduction in reproductive behavior. Scientists from the University of California, Riverside, wanted to investigate the effects of anthropogenic noise on endocrine and reproductive function in the White’s tree frog (Litoria caerulea). Kristine Kaiser et al. (2015) used recordings of frogs’ croaking as well as traffic noise to expose two groups of male frogs to different conditions nightly for one week. For one group they exposed frogs to the chorus of croaking only and for the other group they exposed frogs to croaking noises overlaid with traffic noise.

White’s tree frog (Litoria caerulea)

What Kaiser et al. (2015) found was that the group exposed to traffic noise had significantly higher level of corticosterone (a glucocorticoid produced in response to stress) than the group not exposed to traffic noise. Additionally, male frogs exposed to traffic noise had a significantly lower sperm count and sperm viability.

What does all this mean? Urban noise isn’t only affecting us while we are trying to sleep or study, it also affects wild animals and their important biological functions. Kaiser et al. (2016) gave direct empirical evidence that these noises can stress frogs out, as well as lower their reproductive ability. This contribution towards disentangling the complex effects of chronic anthropogenic stress can help us understand and predict how animals are responding to a changing world.

References

Bergen F, Abs M, 1997. Etho-ecological study of the singing activity of the Blue Tit (Parus caeruleus), Great Tit (Parus major) and Chaffinch (Fringilla coelebs). J Ornithol 138:451-467.

Brumm H, 2004. The impact of environmental noise on song amplitude in a territorial bird. J Anim Ecol 73:434-440.

Brumm H, Slater PJB, 2006. Ambient noise, motor fatigue, and serial redundancy in chaffinch song. Behav Ecol Sociobiol 60:475-481.

Kaiser K, Devito J, Jones CG, Marentes A, Perez R, Umeh L, Weickum RM, McGovern KE, Wilson EH, Saltzman W, 2015. Effects of anthropogenic noise on endocrine and reproductive function in White’s treefrog, Litoria caerulea. Conserv Physiol 3(1)

Parsons, M.J., Salgado Kent, C.P., Recalde-Salas, A. and McCauley, R.D., 2016. Fish choruses off Port Hedland, Western Australia. Bioacoustics, pp.1-18.

Slabbekoorn H, Ripmeester EAP, 2008. Birdsong and anthropogenic noise: implications and applications for conservation. Mol Ecol 17:72-83.

Video and Photo credits

Video: Fish chorus – video upload via user “Amazing Zoology”

Photo: White’s tree frog – www.backwaterreptiles.com