A Case Study in Scientific Inquiry: Investigating Coat Coloration in Mouse Populations

Different coloration in beach and inland populations of Peromyscus polionotus.
Source: Urry, Lisa A.. Campbell Biology (p. 20). Pearson Education. Kindle Edition.

A Case Study in Scientific Inquiry: Investigating Coat Coloration in Mouse Populations (Campbell Biology)

Our case study begins with a set of observations and inductive generalizations. Color patterns of animals vary widely in nature, sometimes even among members of the same species. What accounts for such variation? As you may recall, the two mice depicted at the beginning of this chapter are members of the same species (Peromyscus polionotus), but they have different color patterns and reside in different environments. The beach mouse lives along the Florida seashore, a habitat of brilliant white sand dunes with sparse clumps of beach grass. The inland mouse lives on darker, more fertile soil farther inland. Even a brief glance at the photographs above reveals a striking match of mouse coloration to its habitat. The natural predators of these mice, including hawks, owls, foxes, and coyotes, are all visual hunters (they use their eyes to look for prey). It was logical, therefore, for Francis Bertody Sumner, a naturalist studying populations of these mice in the 1920s, to form the hypothesis that their coloration patterns had evolved as adaptations that camouflage the mice in their native environments, protecting them from predation.

Who is Francis Bertody Sumner? Francis Bertody Sumner (1874-1945), was a professor of Biology, and ichthyologist, at Scripps Institution of Oceanography. Sumner’s name will probably remain most closely and most favorably associated with his longest research, the analysis of speciation in mice of the genus Peromyscus, but most of his separate studies were conducted on fishes. He made significant contributions on the mechanism of color change in fishes and his research on color adaptation in flounders opened a new field.

The researchers built hundreds of models of mice and spray-painted them to resemble either beach or inland mice, so that the models differed only in their color patterns. The researchers placed equal numbers of these model mice randomly in both habitats and left them overnight. The mouse models resembling the native mice in the habitat were the control group (for instance, light-colored mouse models in the beach habitat), while the mouse models with the non-native coloration were the experimental group (for example, darker models in the beach habitat). The following morning, the team counted and recorded signs of predation events, which ranged from bites and gouge marks on some models to the outright disappearance of others. Judging by the shape of the predators’ bites and the tracks surrounding the experimental sites, the predators appeared to be split fairly evenly between mammals (such as foxes and coyotes) and birds (such as owls, herons, and hawks).

For each environment, the researchers then calculated the percentage of predation events that targeted camouflaged models. The results were clear-cut: Camouflaged models showed much lower predation rates than those lacking camouflage in both the beach habitat (where light mice were less vulnerable) and the inland habitat (where dark mice were less vulnerable). The data thus fit the key prediction of the camouflage hypothesis.

What is cryptic coloration? Cryptic coloration allows an organism to match its background and hence become less vulnerable to predation or recognition by prey.


Charles Darwin and Natural Selection


Urry, Lisa A.. Campbell Biology. Pearson Education. Kindle Edition. https://www.pearson.com/us/higher-education/series/Campbell-Biology-Series/2244849.html




Related Research

Research Article: Facial shape differences between rats selected for tame and aggressive behaviors

Date Published: April 3, 2017 Publisher: Public Library of Science Author(s): Nandini Singh, Frank W. Albert, Irina Plyusnina, Lyudmila Trut, Svante Pӓӓbo, Katerina Harvati, Sergio Pellis. http://doi.org/10.1371/journal.pone.0175043 Abstract: Domestication has been consistently accompanied by a suite of traits called the domestication syndrome. These include increased docility, changes in coat coloration, prolonged juvenile behaviors, modified function … Continue reading

Research Article: Coloration and the Genetics of Adaptation

Date Published: September 18, 2007 Publisher: Public Library of Science Author(s): Nicholas I Mundy Abstract: Coat color is often used as camouflage and so has evolutionary benefit. How is coat color determined? Partial Text: How do organisms adapt to new environments? The popular conception of the adaptive process generally runs like this: A mutation arises … Continue reading

Research Article: Carotenoid coloration and health status of urban Eurasian kestrels (Falco tinnunculus)

Date Published: February 8, 2018 Publisher: Public Library of Science Author(s): Petra Sumasgutner, Marius Adrion, Anita Gamauf, Petra Quillfeldt. http://doi.org/10.1371/journal.pone.0191956 Abstract: As the world experiences rapid urban expansion, natural landscapes are being transformed into cities at an alarming rate. Consequently, urbanization is identified as one of the biggest environmental challenges of our time, yet we … Continue reading

Research Article: Carotenoid-based coloration predicts both longevity and lifetime fecundity in male birds, but testosterone disrupts signal reliability

Date Published: August 23, 2019 Publisher: Public Library of Science Author(s): Alejandro Cantarero, Lorenzo Pérez-Rodríguez, Ana Ángela Romero-Haro, Olivier Chastel, Carlos Alonso-Alvarez, William J. Etges. http://doi.org/10.1371/journal.pone.0221436 Abstract: Sexual selection promotes the evolution of conspicuous animal ornaments. To evolve as signals, these traits must reliably express the “quality” of the bearer, an indicator of individual fitness. … Continue reading

Research Article: Physiological and transcriptomic analysis of yellow leaf coloration in Populus deltoides Marsh

Date Published: May 21, 2019 Publisher: Public Library of Science Author(s): Shuzhen Zhang, Xiaolu Wu, Jie Cui, Fan Zhang, Xueqin Wan, Qinglin Liu, Yu Zhong, Tiantian Lin, Siva Ramamoorthy. http://doi.org/10.1371/journal.pone.0216879 Abstract: Populus deltoides Marsh has high ornamental value because its leaves remain yellow during the non-dormant period. However, little is known about the regulatory mechanism … Continue reading

Research Article: A novel body coloration phenotype in Anolis sagrei: Implications for physiology, fitness, and predation

Date Published: December 31, 2018 Publisher: Public Library of Science Author(s): Yasmeen R. Erritouni, Beth A. Reinke, Ryan Calsbeek, Michael Sears. http://doi.org/10.1371/journal.pone.0209261 Abstract: In animals, color signals that convey information about quality are often associated with costs linked to the expression of coloration and may therefore be honest signals of sender quality. Honest indicators are … Continue reading