Rodents, the incredibly versatile creatures, have always piqued the interest of researchers. From their digging behaviors to their senses, rodents display a variety of captivating adjustments that aid their survival in different habitats. At the core of their abilities lie the adaptations in their brains and sensory faculties which play a role in their daily existence. In this piece we set out on a journey through the complexities of neurobiology illuminating the methods by which these small mammals perceive and engage with their environment.
The brain’s adaptability to changing conditions
One feature of brain biology is neuroplasticity, which is the brain’s ability to adapt to outside stimuli. Because of their versatility, rodents can easily navigate across complex situations and grip objects. This capacity is particularly apparent in brain areas associated with memory and learning, such as the neocortex and hippocampal regions.
Studies have shown that exposing rodents to experiences, social interaction and physical activity can cause both anatomical and functional changes in their brains. Increased neurogenesis, improved connections, and modifications in neurotransmitter activities are the end results of these transformations, which strengthen resilience against stress and improve skills.
Sensory adaptations: Accurately traversing the world
Olfaction: To identify food sources, avoid predators and interact with other rodents, rodents mostly rely on their sense of smell. Their sensory modifications are perfectly matched to their ecological niche, giving them exceptionally accurate perception of minute environmental cues. The highly developed olfactory system of rodents is evidenced by the abundance of olfactory receptor genes and the presence of specific brain regions like the olfactory cortex and bulb. Rodents’ excellent sense of smell is crucial to their survival in complicated habitats because it enables them to detect pheromones, follow scent trails and locate possible food sources across great distances.
Petrosal lobule: The petrosal lobule is important for stabilizing eye movements, pursuit tracking, and ocular motor learning. This structure is part of the vestibulocerebellum, which is responsible for processing sensory information about balance and spatial orientation, as well as coordinating eye movements. It is critical for rodents’ consistent and accurate eye movements during a variety of visual tasks, including monitoring moving objects and adapting to changes in the visual environment. Dysfunction of this cerebellum region might result in impaired eye movement control and coordination.
Hearing: Rodents have extremely sensitive auditory systems that enable them to detect a wide range of frequencies, much exceeding the capability of the human ear. Their hearing is exquisitely developed to perceive noises in the ultrasonic spectrum, allowing them to recognize high-pitched calls given by predators and prey. One distinguishing trait of rat hearing is their ability to pinpoint sounds with exceptional accuracy. Despite their small size, mice can reliably identify the source of a sound, a talent required for survival in their frequently deadly environments. This capacity is enabled by the unique structure of their ears, such as the auditory bulla and cochlea, as well as the sophisticated neuronal networks in their brains. Hearing is important in almost every aspect of rodent activity, including foraging, mating and avoiding predators. Rodents interact with one another using vocalizations, which are ultrasonic cries that carry information about their identification, social standing and reproductive state. These cries are often undetectable by human ears, yet they are critical for sustaining social cohesion in rodents’ populations.
Conclusion
The adaptability of rodents in rewiring their brain structures and sensory systems across environmental gradients is a testament to the remarkable evolutionary processes that shape life on Earth. From the bustling metropolis to the remote wilderness, rodents continue to fascinate researchers with their ability to thrive in diverse habitats. Understanding the intricacies of rodent adaptation not only sheds light on fundamental principles of evolutionary biology but also offers insights into potential avenues for biomedical research. As we delve deeper into the mysteries of rodent adaptation, we uncover a world of wonders waiting to be explored.
References
Bertrand, O.C., Püschel, H.P., Schwab, J.A., Silcox, M.T. & Brusatte, S.L. 2021. The impact of locomotion on the brain evolution of squirrels and close relatives. Communications Biology, 4, Art. 460. https://doi.org/10.1038/s42003-021-01887-8
Nengovhela, A., Ivy, C.M., Scott, G.R., Denys C. & Taylor, P.J. 2023. Counter-gradient variation and the expensive tissue hypothesis explain parallel brain size reductions at high elevation in cricetid and murid rodents. Scientific Reports, 13, Art. 5617. https://doi.org/10.1038/s41598-023-32498-4
Neves, C.N & Pillay, N. 2022. Variation in brain volume in nine populations and three taxa of the African striped mouse Rhabdomys. Journal of Morphology, 283, 618–636. https://doi.org/10.1002/jmor.21463
Taylor, P.J., Nengovhela, A., Denys, C., Scott, G.R. & Ivy, C.M. 2024. Adaptation in brain structure, respiratory and olfactory structures across environmental gradients in African and North American muroid rodents. Integrative Zoology, 19, 165–181. https://doi.org/10.1111/1749-4877.12788
Figure 1: Virtual endocast of the early Oligocene squirrel Cedromus wilsoni: a, lateral view inside a solid cranium; b, lateral view inside a translucent cranium; c, lateral view with the different brain regions; d, dorsal view; e, ventral view. nx, neocortex, ob, olfactory bulb, pl, petrosal lobule. (After Bertrand et al. 2021)
Figure 2: The endocast of the rodent inner ear (Image: A Nengovhela).
