Summary: A new study reveals that female mountain chickadees within monogamous pairings proactively cheat on their partners with males that exhibit superior spatial intelligence. The research used automated “smart” feeder arrays to track spatial learning errors in wild birds. Genetic analysis of over three breeding seasons showed that 70% of nests contained extra-pair young, overwhelmingly sired by males with elite memory skills.
High-cognition males sired up to seven extra-pair young annually and fledged heavier, more resilient chicks. Notably, females with poorer cognitive scores were the most likely to seek these trysts, demonstrating a calculated evolutionary strategy to secure highly heritable survival genes for their offspring.
Key Facts
- Intellectual Infidelity: Socially monogamous female mountain chickadees actively seek out extra-pair partners with superior spatial learning and memory compared to their chosen social mates.
- The “Smart” Feeder Test: Individual cognitive performance was mapped using automated bird feeders programmed to reward birds only at specific locations; fewer spatial tracking errors equated to higher cognitive fitness.
- Massive Extra-Pair Rates: Over a three-year span, 70% of all monitored nests contained extra-pair young, accounting for roughly 33% of the entire sampled chick population.
- The Elite Sires: Males displaying top-tier spatial memory sired six to seven extra-pair young per year without suffering any loss of paternity or chick quality within their own home nests.
- Compensatory Mating: Females who performed poorly on spatial cognition tests were significantly more likely to cheat, indicating a drive to supplement their own genetic shortcomings.
- Heavier Fledglings: Beyond genetic inheritance, males with advanced cognitive skills produced heavier chicks overall, directly increasing their survival rates and entry into the future breeding pool.
Source: eLife
Female chickadees living in monogamous mating systems will proactively seek out males that have better cognitive skills than their nestmate, according to new findings.
The research, published today as a Reviewed Preprint in eLife, is described by the editors as an important study using robust genetic analyses and experimental design, providing compelling evidence that females seeking out extra-pair copulations prefer males with strong spatial cognition, and that these males have a reproductive advantage over other males.
Across animal species, females commonly mate with more than one male, even in monogamous mating systems. These so-called extra-pair copulations can increase the fitness of offspring via several mechanisms, including genetic benefits. Understanding the factors that influence choice of mate and the consequences of these decisions on survival and fitness is a central focus of evolutionary biology research.
“When it comes to selecting a mate, females tend to be the ‘choosier’ sex due to their inherent investment. Females seek ‘high-quality’ males to increase the likelihood of successful reproduction, good parental care, and the chance that their offspring inherit ‘good’ genes,” says lead author Carrie Branch, Assistant Professor at Western University, Ontario, Canada.
“Cognitive abilities such as spatial learning and memory allow animals to succeed in variable environments and can be directly inherited and shaped by natural selection, but there is little evidence to show that females choose males with better cognitive abilities.”
To address this, the team followed a population of wild North American mountain chickadees: socially monogamous, non-migratory birds that rely on specialized spatial cognition to recover food stores. They used ‘smart’ feeder arrays – programmed so that only one location per chickadee would result in a rewarding sunflower seed – to assess individual spatial cognition.
The more errors a chickadee made in relocating the food source, the lower their cognitive ability. Alongside this, the team quantified extra-pair paternity over three breeding seasons and compared the spatial cognition skills of the extra-pair males with those of the social male they cuckolded.
Across the three-year study, around a third of the offspring sampled were sired by extra-pair males and 70% of nests had at least one chick resulting from extra-pair copulation (extra-pair young). The researchers found that males with better spatial learning and memory abilities (fewer location errors in the food recovery trials) sired more extra-pair young. In fact, those males that performed best in the cognition tests may sire between six and seven extra-pair young a year, and the age of the males had no bearing on the number of extra-pair young they sired.
The team next looked at the reproductive fitness of the males and how this related to their spatial cognition skills. Males that sired extra-pair young did not appear to lose any reproductive fitness in their own nests, as there was no difference in the number of chicks or chick mass between the extra-pair males and the social males – although males with better spatial cognition raised heavier young overall.
Importantly, as the team hypothesised, extra-pair males had better spatial learning and memory abilities than the social males they cuckolded, even though there was no significant difference in age. This finding suggests that females may preferentially mate with males that have better spatial cognition than their social mate.
However, the likelihood of being cuckolded was not directly related to the social male’s cognitive skills. Instead, females that performed worse in the cognitive tests were more likely to have extra-pair young in their nests, suggesting that females might also seek males in response to their own cognitive deficiencies.
“Our results show that female choice contributes to the evolution of spatial cognitive abilities in a species that stores and recovers thousands of food items and relies on spatial cognition for survival,” concludes senior author Vladimir Pravosudov, Professor of Biology at the University of Nevada, Reno, US.
“Males with better spatial cognition sired more young and fledged heavier chicks, which are more likely to survive and enter the breeding population. Our findings add to the evidence supporting natural selection based on spatial cognitive abilities in wild chickadees.”
Key Questions Answered:
A: Unlike migratory birds that fly south when winter hits, mountain chickadees are non-migratory residents of harsh, variable environments. To survive the freezing months, they cache thousands of individual food items across vast territories. Because they don’t just defend a single pile of food, they must remember the exact coordinates of thousands of hidden seeds. In this ecosystem, a failure of spatial memory is a direct death sentence; if a chickadee cannot remember where it hid its food, it starves.
A: The research team deployed sophisticated, automated “smart” feeder arrays directly into the wild bird population. Each chickadee was outfitted with a tiny radio frequency identification (RFID) tag. The feeder array was programmed so that for any given bird, only one specific feeder slot out of the group would unlock and reward them with a sunflower seed. The scientists tracked how many mistakes each bird made by landing on the wrong slots before finding their designated cache, giving them an incredibly precise, error-based metric of each bird’s spatial learning and memory.
A: This is one of the most fascinating nuances of the study. The likelihood of a nest being cuckolded wasn’t tied to how dumb the social male was, but rather how poorly the female performed on the memory tests. This suggests that females with weak spatial memory are acutely aware of their own survival liabilities. To prevent their offspring from inheriting poor foraging and memory traits, they actively seek out elite “genius” males for extra-pair copulations as an evolutionary insurance policy to upgrade the genetic quality of their brood.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this animal neuroscience and mating research news
Author: Emily Packer
Source: eLife
Contact: Emily Packer – eLife
Image: The image is credited to Vladimir Pravosudov (CC BY 4.0)
Original Research: Open access.
“Male chickadees with better spatial cognition sire more extra-pair young” by Branch CL, Sonnenberg BR, Welklin JF, Butcher BG, Heinen VK, Pitera AM, Benedict LM, Bridge ES, Lovette IJ, Webster MS, Pravosudov VV. eLife
DOI:10.7554/eLife.110905.1
Abstract
Male chickadees with better spatial cognition sire more extra-pair young
Across animal taxa, females commonly mate with more than one male, even in monogamous mating systems. These extra-pair (EP) copulations and resulting young may increase the fitness of the female via a variety of mechanisms, including genetic benefits.
North American chickadees provide an interesting system to study the role of sexual selection via EP paternity, because they are socially monogamous, nonmigratory birds that rely on spatial cognition to recover food stores and variation in spatial cognition is associated with increased survival, longer lifespan, and is heritable.
Given spatial cognitive abilities are heritable and associated with direct survival benefits, these abilities may be under sexual selection if males with better spatial abilities sire more offspring and females prefer to mate with such males. We aimed to address these predictions by quantifying extra-pair paternity and comparing spatial abilities of EP males to those of the social male they cuckold in a wild population of mountain chickadees (Poecile gambeli).
We found that 1. males with better spatial cognitive abilities have more EP young and produce heavier offspring in their own nests compared to their poorer performing counterparts, and 2. EP males have significantly better spatial cognition than the social males they cuckolded.
These results suggest that sexual selection is involved in the evolution of spatial cognitive abilities in food-caching chickadees and are consistent with the good genes hypothesis, which posits that females gain indirect genetic benefits via EP young.
