Inherent behavioural traits enable a widespread lizard to cope with urban life

The "Seven Deadly Sins" of Neophobia Experimental Design

Neophobia, an aversive response to novelty, is a behavior with critical ecological and evolutionary relevance for wild populations because it directly influences animals' ability to adapt to new environments and exploit novel resources. Neophobia has been described in a wide variety of different animal species from arachnids to zebra finches. Because of this widespread prevalence and ecological importance, the number of neophobia studies has continued to increase over time. However, many neophobia studies (as well as many animal behavior studies more generally) suffer from one or more of what we have deemed the "seven deadly sins" of neophobia experimental design. These "sins" include: (1) animals that are not habituated to the testing environment, (2) problems with novel stimulus selection, (3) non-standardized motivation, (4) pseudoreplication, (5) lack of sufficient controls, (6) fixed treatment order, and (7) using arbitrary thresholds for data analysis. We discuss each of these potential issues in turn and make recommendations for how to avoid them in future behavior research. More consistency in how neophobia studies are designed would facilitate comparisons across different populations and species and allow researchers to better understand whether neophobia can help explain animals' responses to human-altered landscapes and the ability to survive in the Anthropocene.

Temporal repeatability of behaviour in a lizard: implications for behavioural syndrome studies

It is well established that, across taxa, individuals within populations exhibit consistent differences in their behaviour across time and/or contexts. Further, the functional coupling of traits may result in the formation of a behavioural syndrome. Despite extensive evidence on the existence of consistent among-individual differences in behaviour and behavioural syndromes in the animal realm, these findings are predominately based upon short-term assessments, leading to questions regarding their stability over longer periods. Understanding if these estimates are temporally stable would allow predictions of individual behaviour to be made using short-term repeated measures. Here, we used 57 adult male delicate skinks (Lampropholis delicata) to evaluate the stability of behavioural variation observed both among (animal personality and behavioural plasticity) and within individuals (behavioural predictability), as well as behavioural syndromes, across short (four weeks) and long (five months) timeframes. To do so, we repeatedly assayed activity, exploration, and boldness five times per each individual. Overall, our study revealed complex patterns of behavioural variation and trait (co)variation over time. Activity was always repeatable across time intervals, whereas behavioural differences among individuals in exploration and boldness were not consistent. Yet a behavioural syndrome between activity and exploration was detected at both shorter and longer temporal scales, suggesting that syndrome structure in these traits does not vary as a function of time. Our findings indicate that, at least for some traits (e.g. activity) and studies, short-term measures may be adequate in serving as a proxy for long-term variation in individual behaviour, and to reveal the existence of behavioural syndromes at the population level.

How do the physiological traits of a lizard change during its invasion of an oceanic island?

Physiology is crucial for the survival of invasive species in new environments. Yet, new climatic conditions and the limited genetic variation found within many invasive populations may influence physiological responses to new environmental conditions. Here, we studied the case of the delicate skinks (Lampropholis delicata) invading Lord Howe Island (LHI), Australia. On LHI, the climate is different from the mainland source of the skinks, and independent introduction events generated invasive populations with distinct genetic backgrounds. To understand how climate and genetic background may shape physiological responses along biological invasions, we compared the physiological traits of a source and two invasive (single-haplotype and multi-haplotype) populations of the delicate skink. For each population, we quantified physiological traits related to metabolism, sprint speed, and thermal physiology. We found that, for most physiological traits analysed, population history did not influence the ecophysiology of delicate skinks. However, invasive populations showed higher maximum speed than the source population, which indicates that locomotor performance might be a trait under selection during biological invasions. As well, the invasive population with a single haplotype was less cold-tolerant than the multi-haplotype and source populations. Our results suggest that limited genetic variability and climate may influence physiological responses of invasive organisms in novel environments. Incorporating the interplay between genetic and physiological responses into models predicting species invasions can result in more accurate understanding of the potential habitats those species can occupy.

Metropolitan lizards? Urbanization gradient and the density of lagartixas (Tropidurus hispidus) in a tropical city

Urbanization, with its cohort of environmental stressors, has a dramatic effect on wildlife, causing loss of biodiversity and decline in population abundance customarily associated with increasing levels of impervious surface and fragmentation of native habitats. Some studies suggest that faunal species from open habitats, and with higher abundance in natural environments, seem more likely to tolerate and live in urban environments. Here I evaluate how the level of urbanization affects lagartixas (Tropidurus hispidus) one of the most common lizards found in open vegetation ecosystems in NE Brazil. I surveyed a total of 47 transects across sites that differed in proportion of impervious surface (high, mild, peri-urban, and rural). I also collected specific biotic (herbaceous cover, tree, and arthropod abundance) and abiotic (amount of shelters and impervious surfaces) factors that could affect lagartixas abundance. Ants were the most common arthropod both in the rural and urban environment. Lagartixas thrive in urban environments, and trees and shelter were key predictors of their abundance. Lagartixas show a clear association with use of artificial structures. The low densities of lagartixas in rural areas and higher density in urbanized areas suggest that they colonized urban areas due to the hard surfaces and they probably are not exploiting a novel habitat, but somewhat responding to conditions resembling those in which they evolved. Finally, lagartixas are extremely common in tropical cities, they have a suite of features that are associated with selective pressures in cities and they might play a key functional role in urban ecosystems making this lizard an excellent system for the study of ecology and adaptation to the urban environments.

Does city life reduce neophobia? A study on wild black-capped chickadees

As human populations increase and city borders grow, many animals have to modify foraging behaviors in order to exploit evolutionarily novel urban food sources that could aid their survival. Neophobia, the fear of novelty, can lead to missed opportunities in these cases. Here, we studied the novelty response of wild animals in ecologically relevant conditions while controlling for individual characteristics and potential differences in foraging group size. We predicted that urban black-capped chickadees (Poecile atricapillus) would be more likely to initially contact novelty than rural chickadees and that subordinates and juveniles would be more likely to first contact novelty than dominants and adults, respectively. We ran replicated experiments using three novelty types (object, color, or food) on six sites, during which we registered feeder choice of 71 tagged individuals. We found that urban chickadees showed less neophobia than their rural counterparts, the latter having a higher probability of initially contacting the familiar feeder before approaching the novel feeder. There was no significant effect of an individual’s dominance, age, or sex on its first choice of feeder, nor was there any effect of novelty type. Overall, our results suggest that urban chickadees exhibit less neophobia than their rural counterparts because they have generally learned to tolerate novelty in their habitat, they have adapted to live in an environment that rewards low neophobia, and/or they are less reluctant to use feeders at new locations.

Do the Calls of a Bird, the Noisy Miner (Manorina melanocephala), Need Adjustment for Efficient Communication in Urban Anthropogenic Noise?

Simple Summary

A common feature of urban environments is constant, low frequency, anthropogenic noise. To communicate effectively acoustically in this environment requires avoidance of sound masking by this background noise. Research suggests that some animals can adjust their vocalizations so that they lie outside the main frequency range of urban anthropogenic noise, whilst others may produce sound signals that naturally avoid masking and therefore do not require adjustment. To date, research in this area has tended to focus on adjustment to complex songs, rather than simpler calls. The Noisy miner, Manorina melanocephala, is a very successful avian urban colonizer that uses calls in its acoustic communication. We compared the calls of this species in both urban and rural populations. Of all calls compared, only those that lay within the main frequency range of anthropogenic noise (1–2 kHz) showed shifts in minimum sound frequency in urban individuals, but these frequency shifts were notably small and insufficient to entirely preclude masking by urban noise. However, several Noisy miner calls had frequencies of more than 2 kHz that lay outside the main frequency range of urban anthropogenic noise (>2 kHz), suggesting intriguingly that this species may be inherently well-suited to communicating vocally in urban settings, which may be one of the keys to its success as an urban colonizer.

Abstract

Urban environments are characteristically noisy and this can pose a challenge for animals that communicate acoustically. Although evidence suggests that some birds can make acoustic adjustments that preclude masking of their signals in high-disturbance environments such as cities, studies to date have tended to focus on acoustic signals important in mate attraction (e.g., songs). Far less attention has been given to the impact of urban noise on other kinds of calls. To redress this, we compared a range of different vocalizations (encompassing alarm calls, begging calls and parent response calls) among urban and rural individuals of a successful Australian ‘urban adapter’, the Noisy miner, Manorina melanocephala. We found that urban miners had significantly higher minimum sound frequencies for calls with low base-frequencies (<2 kHz); however, calls with base-frequencies ‘naturally’ above the main frequency range of urban noise (>2 kHz) had the same minimum frequency in urban and rural birds. Dominant frequency and call duration did not differ between urban and rural individuals. Although urban Noisy miners exhibited differences from rural individuals in the minimum frequency of calls, this shift was not large enough to avoid masking from low-frequency, anthropogenic noise. Nevertheless, our findings suggest that the calls of Noisy miners may be naturally well suited to being heard in noisy urban environments by having (a) dominant frequencies higher than low-level, anthropogenic noise and (b) several important call-types with frequencies above the main frequency range associated with urban noise.