Dakota "Cody" McCoy is a Stanford Science Fellow (also supported by the NSF PRFB) who recently completed her PhD in Evolutionary Biology at Harvard University. Previously, she attended Oxford University as a Rhodes Scholar to study environmental policy. Combining applied physics with biological methods, she studies the functions and origins of optical adaptations in nature. For example, her work on “super black” birds and spiders has driven novel solar technology research, inspired recent studies of light manipulation in several animals, and will soon appear in a forthcoming United Nations booklet on bioinspiration. She also researches the unusual health risks of pregnancy for humans. Cody hails from Pittsburgh, greatest city in the USA, where she grew up with four siblings and four dogs.
Honors & Awards
Stanford Science Fellow, Stanford University (7/1/2021-7/1/2024)
NSF Postdoctoral Research Fellow in Biology, National Science Foundation (7/1/2021-7/1/2023)
Trail-Crisp Medalist, The Linnean Society (2021)
National Defense Science and Engineering Graduate Fellow, USA Department of Defense (9/1/2015-5/23/2021)
Ashford Fellow, Theodore H. Ashford Fellowship (9/1/2015-5/23/2021)
Rhodes Scholar, The Rhodes Trust (9/1/2013-6/1/2015)
After short interbirth intervals, captive callitrichine monkeys have higher infant mortality.
1800; 25 (1): 103724
Life history theory predicts a trade-off between the quantity and quality of offspring. Short interbirth intervals-the time between successive births-may increase the quantity of offspring but harm offspring quality. In contrast, long interbirth intervals may bolster offspring quality while reducing overall reproductive output. Further research is needed to determine whether this relationship holds among primates, which have intensive parental investment. Using Cox proportional hazards models, we examined the effects of interbirth intervals (short, normal, or long) on infant survivorship using a large demographic dataset (n= 15,852) of captive callitrichine monkeys (marmosets, tamarins, and lion tamarins). In seven of the nine species studied, infants born after short interbirth intervals had significantly higher risks of mortality than infants born after longer interbirth intervals. These results suggest that reproduction in callitrichine primates may be limited by physiologic constraints, such that short birth spacing drives higher infant mortality.
View details for DOI 10.1016/j.isci.2021.103724
View details for PubMedID 35072012
Finite-difference Time-domain (FDTD) Optical Simulations: A Primer for the Life Sciences and Bio-Inspired Engineering.
Micron (Oxford, England : 1993)
2021; 151: 103160
Light influences most ecosystems on earth, from sun-dappled forests to bioluminescent creatures in the ocean deep. Biologists have long studied nano- and micro-scale organismal adaptations to manipulate light using ever-more sophisticated microscopy, spectroscopy, and other analytical equipment. In combination with experimental tools, simulations of light interacting with objects can help researchers determine the impact of observed structures and explore how variations affect optical function. In particular, the finite-difference time-domain (FDTD) method is widely used throughout the nanophotonics community to efficiently simulate light interacting with a variety of materials and optical devices. More recently, FDTD has been used to characterize optical adaptations in nature, such as camouflage in fish and other organisms, colors in sexually-selected birds and spiders, and photosynthetic efficiency in plants. FDTD is also common in bioengineering, as the design of biologically-inspired engineered structures can be guided and optimized through FDTD simulations. Parameter sweeps are a particularly useful application of FDTD, which allows researchers to explore a range of variables and modifications in natural and synthetic systems (e.g., to investigate the optical effects of changing the sizes, shape, or refractive indices of a structure). Here, we review the use of FDTD simulations in biology and present a brief methods primer tailored for life scientists, with a focus on the commercially available software Lumerical FDTD. We give special attention to whether FDTD is the right tool to use, how experimental techniques are used to acquire and import the structures of interest, and how their optical properties such as refractive index and absorption are obtained. This primer is intended to help researchers understand FDTD, implement the method to model optical effects, and learn about the benefits and limitations of this tool. Altogether, FDTD is well-suited to (i) characterize optical adaptations and (ii) provide mechanistic explanations; by doing so, it helps (iii) make conclusions about evolutionary theory and (iv) inspire new technologies based on natural structures.
View details for DOI 10.1016/j.micron.2021.103160
View details for PubMedID 34678583
Microstructures amplify carotenoid plumage signals in tanagers
2021; 11 (1): 8582
Brilliantly-colored birds are a model system for research into evolution and sexual selection. Red, orange, and yellow carotenoid-colored plumages have been considered honest signals of condition; however, sex differences in feather pigments and microstructures are not well understood. Here, we show that microstructures, rather than carotenoid pigments, seem to be a major driver of male-female color differences in the social, sexually-dimorphic tanager genus Ramphocelus. We comprehensively quantified feather (i) color (using spectrophotometry), (ii) pigments (using liquid chromatography-mass spectrometry (LC-MS)), and (iii) microstructures (using scanning electron microscopy (SEM) and finite-difference time-domain (FDTD) optical modeling). Males have significantly more saturated color patches than females. However, our exploratory analysis of pigments suggested that males and females have concordant carotenoid pigment profiles across all species (MCMCglmm model, female:male ratio = 0.95). Male, but not female, feathers have elaborate microstructures which amplify color appearance. Oblong, expanded feather barbs in males enhance color saturation (for the same amount of pigment) by increasing the transmission of optical power through the feather. Dihedral barbules (vertically-angled, strap-shaped barbules) in males reduce total reflectance to generate "super black" and "velvet red" plumage. Melanin in females explains some, but not all, of the male-female plumage differences. Our results suggest that a widely cited index of honesty, carotenoid pigments, cannot fully explain male appearance. We propose that males are selected to evolve amplifiers-in this case, microstructures that enhance appearance-that are not necessarily themselves linked to quality.
View details for DOI 10.1038/s41598-021-88106-w
View details for Web of Science ID 000644194200018
View details for PubMedID 33883641
View details for PubMedCentralID PMC8060279
Embryo Seection and Mate Choice: Can 'Honest Signals' Be Trusted?
TRENDS IN ECOLOGY & EVOLUTION
2020; 35 (4): 308-318
When a measure becomes a target, it often ceases to be a good measure - an effect familiar from the declining usefulness of standardized testing in schools. This economic principle also applies to mate choice and, perhaps surprisingly, pregnancy. Just as females screen potential mates under many metrics, human mothers unconsciously screen embryos for quality. 'Examinees' are under intense selection to improve test performance by exaggerating formerly 'honest' signals of quality. Examiners must change their screening criteria to maintain useful information (but cannot abandon old criteria unilaterally). By the resulting 'proxy treadmill', new honest indicators arise while old degraded indicators linger, resulting in trait elaboration and exaggeration. Hormone signals during pregnancy show extreme evolutionary escalation (akin to elaborate mating displays).
View details for DOI 10.1016/j.tree.2019.12.002
View details for Web of Science ID 000519994500008
View details for PubMedID 32000998
Delayed gratification in New Caledonian crows and young children: influence of reward type and visibility
2020; 23 (1): 71-85
Self-control underlies cognitive abilities such as decision making and future planning. Delay of gratification is a measure of self-control and involves obtaining a more valuable outcome in the future by tolerating a delay or investing a greater effort in the present. Contextual issues, such as reward visibility and type, may influence delayed gratification performance, although there has been limited comparative investigation between humans and other animals, particularly non-primate species. Here, we adapted an automated 'rotating tray' paradigm used previously with capuchin monkeys to test for delay of gratification ability that requires little pre-test training, where the subject must forgo an immediate, less preferred reward for a delayed, more preferred one. We tested New Caledonian crows and 3-5-year-old human children. We manipulated reward types to differ in quality or quantity (Experiments 1 and 2) as well as visibility (Experiment 2). In Experiments 1 and 2, both species performed better when the rewards varied in quality as opposed to quantity, though performed above chance in both conditions. In Experiment 1, both crows and children were able to delay gratification when both rewards were visible. In Experiment 2, 5-year-old children outperformed 3- and 4-year olds, though overall children still performed well, while the crows struggled when reward visibility was manipulated, a result which may relate to difficulties in tracking the experimenters' hands during baiting. We discuss these findings in relation to the role of contextual issues on self-control when making species comparisons and investigating the mechanisms of self-control.
View details for DOI 10.1007/s10071-019-01317-7
View details for Web of Science ID 000491948700001
View details for PubMedID 31630344
View details for PubMedCentralID PMC6981108
Convergent evolution of super black plumage near bright color in 15 bird families
JOURNAL OF EXPERIMENTAL BIOLOGY
2019; 222 (18)
We examined extremely low-reflectance, velvety black plumage patches in 32 bird species from 15 families and five orders and compared them with 22 closely related control species with normal black plumage. We used scanning electron microscopy to investigate microscopic feather anatomy, and applied spectrophotometry and hyperspectral imaging to measure plumage reflectance. Super black plumages are significantly darker and have more broadband low reflectance than normal black plumages, and they have evolved convergently in 15 avian families. Super black feather barbules quantitatively differ in microstructure from normal black feathers. Microstructural variation is significantly correlated with reflectance: tightly packed, strap-shaped barbules have lower reflectance. We assigned these super black feathers to five heuristic classes of microstructure, each of which has evolved multiple times independently. All classes have minimal exposed horizontal surface area and 3D micrometer-scale cavities greater in width and depth than wavelengths of light. In many species, barbule morphology varied between the super black exposed tip of a feather and its (i) concealed base or (ii) iridescently colored spot. We propose that super black plumages reduce reflectance, and flatten reflectance spectra, through multiple light scattering between the vertically oriented surfaces of microscale cavities, contributing to near-complete absorption of light by melanin. All super black plumage patches identified occur adjacent to brilliant colored patches. Super black plumage lacks all white specular reflections (reference points used to calibrate color perception), thus exaggerating the perceived brightness of nearby colors. We hypothesize that this sensory bias is an unavoidable by-product of color correction in variable light environments.
View details for DOI 10.1242/jeb.208140
View details for Web of Science ID 000488952100013
View details for PubMedID 31558610
New Caledonian Crows Behave Optimistically after Using Tools
2019; 29 (16): 2737-+
Are complex, species-specific behaviors in animals reinforced by material reward alone or do they also induce positive emotions? Many adaptive human behaviors are intrinsically motivated: they not only improve our material outcomes, but improve our affect as well [1-8]. Work to date on animal optimism, as an indicator of positive affect, has generally focused on how animals react to change in their circumstances, such as when their environment is enriched [9-14] or they are manipulated by humans [15-23], rather than whether complex actions improve emotional state. Here, we show that wild New Caledonian crows are optimistic after tool use, a complex, species-specific behavior. We further demonstrate that this finding cannot be explained by the crows needing to put more effort into gaining food. Our findings therefore raise the possibility that intrinsic motivation (enjoyment) may be a fundamental proximate cause in the evolution of tool use and other complex behaviors. VIDEO ABSTRACT.
View details for DOI 10.1016/j.cub.2019.06.080
View details for Web of Science ID 000481587900030
View details for PubMedID 31378612
A comparative study of litter size and sex composition in a large dataset of callitrichine monkeys
AMERICAN JOURNAL OF PRIMATOLOGY
2019; 81 (9): e23038
In many birds and mammals, the size and sex composition of litters can have important downstream effects for individual offspring. Primates are model organisms for questions of cooperation and conflict, but the factors shaping interactions among same-age siblings have been less-studied in primates because most species bear single young. However, callitrichines (marmosets, tamarins, and lion tamarins) frequently bear litters of two or more, thereby providing the opportunity to ask whether variation in the size and sex composition of litters affects development, survival, and reproduction. To investigate these questions, we compiled a large dataset of nine species of callitrichines (n = 27,080 individuals; Callithrix geoffroyi, Callithrix jacchus, Cebuella pygmaea, Saguinus imperator, Saguinus oedipus, Leontopithecus chrysomelas, Leontopithecus chrysopygus, Leontopithecus rosalia, and Callimico goeldii) from zoo and laboratory populations spanning 80 years (1938-2018). Through this comparative approach, we found several lines of evidence that litter size and sex composition may impact fitness. Singletons have higher survivorship than litter-born peers and they significantly outperform litter-born individuals on two measures of reproductive performance. Further, for some species, individuals born in a mixed-sex litter outperform isosexually-born individuals (i.e., those born in all-male or all-female litters), suggesting that same-sex competition may limit reproductive performance. We also document several interesting demographic trends. All but one species (C. pygmaea) has a male-biased birth sex ratio with higher survivorship from birth to sexual maturity among females (although this was significant in only two species). Isosexual litters occurred at the expected frequency (with one exception: C. pygmaea), unlike other animals, where isosexual litters are typically overrepresented. Taken together, our results indicate a modest negative effect of same-age sibling competition on reproductive output in captive callitrichines. This study also serves to illustrate the value of zoo and laboratory records for biological inquiry.
View details for DOI 10.1002/ajp.23038
View details for Web of Science ID 000480079200001
View details for PubMedID 31389057
View details for PubMedCentralID PMC6949018
Structurally assisted super black in colourful peacock spiders
PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
2019; 286 (1902): 20190589
Male peacock spiders ( Maratus, Salticidae) compete to attract female mates using elaborate, sexually selected displays. They evolved both brilliant colour and velvety black. Here, we use scanning electron microscopy, hyperspectral imaging and finite-difference time-domain optical modelling to investigate the deep black surfaces of peacock spiders. We found that super black regions reflect less than 0.5% of light (for a 30° collection angle) in Maratus speciosus (0.44%) and Maratus karrie (0.35%) owing to microscale structures. Both species evolved unusually high, tightly packed cuticular bumps (microlens arrays), and M. karrie has an additional dense covering of black brush-like scales atop the cuticle. Our optical models show that the radius and height of spider microlenses achieve a balance between (i) decreased surface reflectance and (ii) enhanced melanin absorption (through multiple scattering, diffraction out of the acceptance cone of female eyes and increased path length of light through absorbing melanin pigments). The birds of paradise (Paradiseidae), ecological analogues of peacock spiders, also evolved super black near bright colour patches. Super black locally eliminates white specular highlights, reference points used to calibrate colour perception, making nearby colours appear brighter, even luminous, to vertebrates. We propose that this pre-existing, qualitative sensory experience-'sensory bias'-is also found in spiders, leading to the convergent evolution of super black for mating displays in jumping spiders.
View details for DOI 10.1098/rspb.2019.0589
View details for Web of Science ID 000468618100009
View details for PubMedID 31088270
View details for PubMedCentralID PMC6532503
Structural absorption by barbule microstructures of super black bird of paradise feathers
2018; 9: 1
Many studies have shown how pigments and internal nanostructures generate color in nature. External surface structures can also influence appearance, such as by causing multiple scattering of light (structural absorption) to produce a velvety, super black appearance. Here we show that feathers from five species of birds of paradise (Aves: Paradisaeidae) structurally absorb incident light to produce extremely low-reflectance, super black plumages. Directional reflectance of these feathers (0.05-0.31%) approaches that of man-made ultra-absorbent materials. SEM, nano-CT, and ray-tracing simulations show that super black feathers have titled arrays of highly modified barbules, which cause more multiple scattering, resulting in more structural absorption, than normal black feathers. Super black feathers have an extreme directional reflectance bias and appear darkest when viewed from the distal direction. We hypothesize that structurally absorbing, super black plumage evolved through sensory bias to enhance the perceived brilliance of adjacent color patches during courtship display.
View details for DOI 10.1038/s41467-017-02088-w
View details for Web of Science ID 000419657800001
View details for PubMedID 29317637
View details for PubMedCentralID PMC5760687
- Speak out against tuition waiver taxes SCIENCE 2017; 358 (6369): 1394
- Speak out against tuition waiver taxes. Science (New York, N.Y.) 2017; 358 (6369): 1395
- Development of boldness and docility in yellow-bellied marmots ANIMAL BEHAVIOUR 2013; 86 (6): 1147-1154
- The Cranial Anatomy of the Miocene Notoungulate Hegetotherium mirabile (Notoungulata, Hegetotheriidae) with Preliminary Observations on Diet and Method of Feeding BULLETIN OF THE PEABODY MUSEUM OF NATURAL HISTORY 2012; 53 (2): 355-374
- Connecticut Birds and Climate Change: Bergmann's Rule in the Fourth Dimension NORTHEASTERN NATURALIST 2012; 19 (2): 323-334