Biology subjects

Makuya, L.

Publications and source records attributed to Makuya, L..

4 recordsLinked to original sources

bioRxiv2025

Thermal Refuges as Extended Phenotypes: Lodge Construction by Bush Karoo Rats

Animal architecture has received considerable attention as an extended phenotype that buffers organisms against environmental harshness. However, few studies have described animal architecture in a representative sample, assessed and then tested its function experimentally. We adopted such an approach for stick lodges built by the bush Karoo rat (Otomys unisulcatus), a solitary rodent inhabiting semi-arid regions of southern Africa. These lodges are among the largest animal-built structures by solitary mammals, yet their structural variation and ecological function remain poorly quantified. We conducted the first population-level survey of all lodges in our 4.5 ha field site to assess external and internal lodge structure, assess their effects on microclimate, and tested experimentally whether lodge size affects microclimate. Lodges were several hundred times larger than their builders and featured complex structure, including basking platforms, nesting, food and latrine chambers. Inside lodges, temperatures were closer to the bush Karoo rats thermoneutral zone and exhibited higher humidity than ambient conditions, which could reduce costs of thermoregulation and reduce water loss. These benefits correlated with initial lodge size and decreased when lodge size was experimentally reduced. Tunnels were often blocked off with thorny branches, possibly to deter snakes. Platforms typically faced eastwards and were regularly used for basking, likely enhancing passive heat gain. We conclude that bush Karoo rat lodges are complex, and costly to build and maintain. They improve thermoregulation and provide predator protection and food storage. Bush Karoo rat lodges (1) are external structures, adding to the builders body (2) are functional, (3) probably increasing fitness, (4) result from behavioural activity, and (5) are likely genetically encoded. We therefore consider them an extended phenotype shaped by ecological pressures and evolutionary history.

animal behavior and cognition↗

bioRxiv2025

Pair-Living Emerged Early in Placental Mammals

It is widely assumed that the first placental mammals were solitary. This assumption has been used as the default in previous comparative studies, but has never been tested independently. Here, we compiled a comprehensive database by reviewing over 14,000 primary peer-reviewed publications on the social organization of the 5,386 extant placental mammal species. We found empirical data for 738 species across 1,478 populations: 354 populations were primarily solitary, 241 populations pair-living and 878 populations group-living. Notably, 383 species (52%) and 580 populations (39%) exhibited intra-specific variation in social organization. Using a Bayesian phylogenetic framework that incorporates intra-specific variation, we show that the ancestral placental mammal - living approximately 160 to 100 million years ago - was not exclusively solitary, but likely displayed intraspecific variation. Pair-living was predicted to account for approximately 26% of ancestral social organisation. Our analysis found that ecology and life history of extant solitary and pair-living mammals was very similar and different from those of group-living mammals. Our results revise prevailing theories of mammalian social evolution, revealing that pair-living emerged early, shifting the focus of mammalian social evolution from the origins of pair-living to the origins of group-living.

evolutionary biology↗

bioRxiv2024

Shared foraging grounds in a solitary rodent: indication for cooperation by kin selection and mutualism?

O_LIKinship is important for understanding the evolution of social behaviour in group living species. However, even solitary living individuals differentiate between kin and non-kin neighbours, which could lead to some form of cooperation, defined as both partners benefitting from each other. A simple form of cooperation is mutualism, where both partners benefit simultaneously. C_LIO_LIHere we tested whether there is mutual tolerance by sharing foraging grounds between kin in a solitary species. This would indicate the possibility of kin selection and mutual cooperation. C_LIO_LIWe used mini-GPS data loggers to investigate range overlap in the solitary bush Karoo rat (Otomys unisulcatus) between kin- and non-kin neighbours. Next, we quantified the extent to which individuals shared foraging grounds containing food plants within their overlapping ranges. Lastly, using step selection functions applied to GPS fixes collected every five minutes, we analysed how individuals moved relative to each other. C_LIO_LIKin-neighbours had larger home range overlap than non-kin neighbours (70.4% vs 29.6%) and shared more of their foraging grounds (63% vs 37%). C_LIO_LITemporal analysis of spatial data found no indication that neighbours avoided each other, independent of kinship. Instead, activity was synchronised. C_LIO_LIIn sum, we found mutual tolerance between neighbours with regards to sharing foraging grounds, and kin shared nearly double as much of their foraging grounds than non-kin. C_LIO_LIThese data can be interpreted as a simple way of mutual cooperation between kin in a solitary species, where both members benefit from sharing a considerable part of their foraging grounds. C_LI

animal behavior and cognition↗

bioRxiv2024

Tolerant mothers: aggression does not explain solitary living in the bush Karoo rat

Many mammal species are thought to adopt solitary living due to mothers becoming intolerant of their adult offspring as well as social intolerance between adults. However, field studies on how solitary mammals interact are rare. Here we show that solitary living can occur without social intolerance. Over three years, we recorded interactions between free living bush Karoo rats (Otomys unisulcatus ) and conducted dyadic encounter experiments between kin and non-kin female neighbours, both in a neutral test arena and in field intruder experiments. Social interactions were rare (N=230 in N=2062 observations), and, when observed, were aggressive in only 34% of the cases. In dyadic encounters, mothers interacted amicably with young offspring. Aggression between mothers and offspring was almost absent. This mother-offspring relationship remained amicable even after the offspring had dispersed. Aggression between neighbouring adult females was low in neutral arena tests, independent of kinship and season. However, in the field, females reacted more aggressively towards non-kin than kin intruders, especially during the breeding season. Tolerance between mothers and adult offspring indicates that aggression is not the mechanism leading to natal dispersal and solitary living. We found a solitary social system characterised by social tolerance, suggesting that dispersal in combination with a lack of social attraction rather than aggression can lead to solitary living.

animal behavior and cognition↗