Does body mass restrict call peak frequency in echolocating bats?

Abstract

1. Echolocation is the ability of some animals to orient themselves through sound emission and interpretation of the echoes. This is bats' main sense for orientation and recognising biotopes that provide food, water, and roosts. It is widely accepted that echolocation call frequency is related to body mass, and this relationship has been described as the 'allometric hypothesis', which proposes a negative correlation between these variables. 2. There is evidence that, in many cases, the allometric hypothesis does not apply. Additionally, studies supporting this hypothesis were done at the family level, resulting in a broad range of correlation values with r ranging from −0.36 to −0.76, and only insectivorous bats were included. Due to the notable exceptions and the lack of a quantitative synthesis of this hypothesis including all echolocating bats, we evaluated the allometric hypothesis of echolocation calls for this group. 3. Using a meta-analysis and phylogenetic generalised least-squares techniques, we evaluated the relationship between echolocation call peak frequency and the body mass of bats. 4. We found a negative relationship between body mass and echolocation call peak frequency for the 85 bat species that were included in our analysis (r = −0.3, p = 0.005). The relationship was consistent when we analysed the data at the insectivorous guild level, and in bats belonging to the families Vespertilionidae, Rhinolophidae, Emballonuridae, and the genus Myotis. However, the wide range of r values suggests that the strength of the relationship between peak frequency and body mass varies within the order Chiroptera. 5. Our results support the allometric hypothesis of sound production in echolocating bats. However, the low coefficient we found suggests that factors other than body mass may influence the peak frequency of echolocation calls produced by bats.

Atmospheric humidity affects global variation of bat echolocation via indirect effects

“…This could simply result from the presence of phyllostomids and other non-insectivorous bat taxa in the full data. Compared to the insectivorous bat taxa, which make up nearly 100% of the aerial hawking subset, there is indeed a weaker association between body mass and peak frequency in phyllostomid and non-insectivorous bats (Jones, 1999;López-Cuamatzi et al, 2020).…”

“…The allometric non-linear relationship between bat peak frequency and body mass has been demonstrated (Heller, 1996;López-Cuamatzi et al, 2020). However, we use the path model that assumes linear relationships between variables and therefore performed natural log (ln) transformation on these variables to achieve linearity.…”

“…Specific humidity represents a combined effect of temperature and relative humidity, both of which increase heat stress by affecting body temperature directly and impeding evaporative cooling, respectively (James, 1970). In addition, a negative association between body size and peak frequency is well-demonstrated in bats (Barclay, 1991;Bogdanowicz et al, 1999;Jones, 1999;Thiagavel et al, 2017;Luo et al, 2019;López-Cuamatzi et al, 2020). Considering this together with the aforementioned association between specific humidity and body size, body size could mediate the indirect effect of specific humidity on peak frequency, as previously suggested by Mutumi et al (2016) (body size constraint hypothesis, Figure 2).…”

Phenotypic traits evolution and morphological traits associated with echolocation calls in cryptic horseshoe bats (Rhinolophidae)

“…Horseshoe bats (Rhinolophidae) emit calls with constant frequency signals (CF), and call duration is relatively long (>30 ms) compared to other bat families with CF calls (such as Hipposideridae), and are able to compensate for the effect of Doppler‐shift (Schnitzler & Denzinger, 2011). Over the course of evolution, the echolocation behavior and hearing systems of bats have adapted to foraging systems, what they eat and how they acquire food (Koselj et al, 2011; Lazure & Fenton, 2011; Jacobs et al, 2014; Cvikel et al, 2015; Jones et al, 2016; Arbour et al, 2019; Brokaw & Smotherman, 2020; López‐Cuamatzi et al, 2020; Giacomini et al, 2021).…”

“…However, while previous studies have focused on the associations between bat skull size and morphology related to echolocation within an evolutionary context (Bogdanowicz et al, 1999; Arbour et al, 2019; Giacomini et al, 2021), little attention to other morphological traits. Body size has been proposed to have constrained echolocation calls in bats, as aerial‐feeding bats must be lighter to fly while echolocating, which is energy costly (López‐Cuamatzi et al, 2020). Higher frequency species generally have a smaller body size (allometric relationship) to facilitate feeding, locomotion, and reproduction success strategies (Dumont, 2007; Roff & Fairbairn, 2007; Jacobs & Bastian, 2018; Moyers‐Arévalo et al, 2020).…”