Overview and general comments:
The current study investigated sleep in wild animals, with a focus on inter- and intra-individual variability under changing environmental conditions. The authors analysed a quite large dataset of 28 wild boars monitored from 2019 to 2021 by means of accelerometers fitted in GPS collars in two different study areas. While the number of monitored animals is large, the mean sample period is quite short (about 3 months).

Taking advantage of detailed information on sleep in domestic pigs coming from laboratory studies, from raw accelerometer data they identified sleep bouts for each wild boar over its monitoring period. The analytic approach used to discriminate sleep behaviour seems robust and reliable, based on the scientific literature on the topic, however, I think that more details are needed to be fully understood by non-specialist readers and to allow replicability of this study (see also detailed comments below).

Once identified sleep bouts, the authors calculated 3 different measures: total daily sleep time - as an estimate of sleep quantity; the number of sleeping bouts over the 24-hour period – as an estimate of sleep efficiency; the duration of the longest sleep bout in the 24-hour period – as an estimate of sleep quality. These three sleep measures, as well as their variance, were analysed by means of double-hierarchical generalized linear mixed-effects models (DHGLM) to investigate the effects of weather, light, and environmental conditions on wild boar sleeping behaviour and its plasticity. The authors used different analyses, which is warranted. I am familiar with, and confident that they appropriately used the linear mixed models. I am less familiar with double-hierarchical generalized linear mixed-effects models and Markov chain Monte Carlo, so would defer to a reviewer with expertise with those techniques.

I found the topic of this paper of great interest, providing one of the first information on sleeping behaviour in the wild. Moreover, the authors used an interesting analytical approach, which may be used in future research on other species in the wild, given the large use of accelerometers in wild animal monitoring. However, as already pointed out, I think that more details on this analytical approach should be provided for its replicability (see details comments below).
Moreover, while I found in this study novel and interesting perspectives in the investigation of wild animal behaviour (i.e., detailed aspects of sleeping behaviour which have been studied only in controlled conditions in the laboratory), I found a lack of a more general overview and consideration of the different aspects of the behavioural ecology of wild animals. Specifically:
1) The authors only marginally considered in their analysis the possible effects of the predator presence. They only made inferences on this topic in the discussion section, to explain differences between the two study sites (L. 403-409). However, they did not provide information on predator presence in the study area section, nor did they consider this topic in the introduction. As I would expect a great influence of the predator on sleeping behaviour in wild animals, in my opinion, more focus should be given to this topic explicitly including this effect in their investigation (for instance, by adding a prediction at the end of the introduction, by including it as a variable in their statistical analysis).
2) They only marginally considered in their investigation the possible effects of the anthropogenic disturbance. The two study areas were characterized by a different human presence (see L. 145-147) and the monitoring period includes the Covid-19 lockdown period, which previous research has shown to strongly affect animal behaviour (e.g., Montgomery et al. 2020). As I would expect an influence of anthropogenic disturbance on wild animals’ sleeping, I think it should be directly included in the investigation by directly quantifying human presence spatially and temporally.
3) They did not take into consideration other aspects of wild boar behaviour, for instance, activity rhythms (diurnality/nocturnality) and activity levels, which I expect to influence sleep. Previous studies have shown variations of wild boar activity in response to weather (temperature, humidity, precipitation), moonlight, and anthropogenic disturbance (e.g. Caley 1997, Cahill, et al. 2003, Keuling et al. 2008, Ohashi et al. 2013, Brivio et al. 2017, Gordigiani et al. 2022). Discussion and comparisons with these studies should be included to give a more general overview of wild boar behavioural responses to environmental conditions.

Specific comments:

L. 143-147: What about the presence of other species in the two study sites? Are there potential predators and/or competitor species in the two areas? Is hunting forbidden in the study areas and their surroundings? More general, information about human disturbance should be provided. Some information is currently reported in the discussion section, but they must be described more in detail here.

L. 152-153: a more detailed description of the accelerometer used in this study should be provided to help all no-specialist readers fully understand your study: How data are recorded by the accelerometer? What kind of data are provided by the accelerometer? In which range? In which units of measure are recorded?

L. 172-173: I think a description of the procedure adopted to calculate the “static acceleration” is needed for the no-specialist readers. I combed through the cited papers (e.g., Wilson et al 2008) but, as I am not used to such kind of data and calculations, I found it hard to understand how the static acceleration was calculated.

L. 173-174: Which procedure did you use to smooth the static acceleration over two seconds?

L. 179-181: Since raw data are not described (for instance, in which unit are recorded?), I found it hard to understand how you calculated the dynamic components of each axis of acceleration.

L. 203-204: moon phase is not a good measure of night illumination, because the moon may be covered by clouds thus affecting actual night brightness. I suggest using in the analysis a measure considering both the moon phase and cloud cover, which should be a better predictor of night brightness (see for instance Brivio et al. 2017, Gordigiani et al. 2021).

L. 222: what “location” is? I guess this represents the study sites (Kostelec and Doupov). If yes, please clearly state this or explain how "location" was defined for each wild boar (for instance, using GPS positions?).

215-228: I have some concerns about the linear effect of temperature. Several studies showed that temperature has a non-linear effect on animal behavioural traits (for instance, locomotory activity, see Brivio et al. 2016, Grignolio et al. 2018). For instance, we could expect that extreme conditions during cold days may negatively affect animal sleep with very low temperatures reducing TST, quality and/or efficiency. Have you considered modelling temperature and other environmental predictors with a non-linear relationship (for instance, by using a second-order polynomial term or by fitting data with Generalized additive models?)

L. 338-344: It would be interesting to know in which part of the day (diurnal or nocturnal phase) sleeping bouts occurred. Most of the available evidence in the literature showed that wild boar is mainly active at night (Saunders and Kay 1991, Caley 1997; Russo et al. 1997, Cahill et al., 2003, Keuling et al., 2008, Brivio et al. 2017, Gordigiani et al. 2022), thus I would expect sleep to occur mostly during diurnal hours. But this should be directly tested with your valuable data. On account of sleeping occurring during the day or the night, I would also expect different effects of environmental factors: air temperature during the day has been shown to have a negative effect on wild boar activity but a positive effect on their nocturnal activity (Brivio et al. 2017). Also, human disturbance (occurring mostly during the day) should have different effects on nocturnal/diurnal sleeping.

L. 384-397: The effect of weather factors should be discussed with a broader perspective on the behavioural ecology of wild boar in the wild, with comparisons with other studies on wild boar behaviour.

L. 393-394: Previous studies have shown a positive effect of night brightness on wild boar activity (e.g., Brivio et al. 2017, Gordigiani et al. 2022), can this explain its negative effect on sleeping?

L. 398-400: Do you have data on females’ reproductive state? Or on the presence of piglets? If yes, it would be interesting to consider them in your investigation, otherwise, I think that this part of the discussion is mostly speculative.

L. 403-414: As previously pointed out, I think that predation risk and anthropogenic disturbance deserve deeper attention, both in the introduction and in the analysis section.

L. 414-424: I think that without a specific analysis of resting site selection, these considerations are speculative only. For instance, localization (close or far away from human activity) of wallows or water bodies strictly depends on the habitat type, study area, etc. Actual temperature, humidity, and precipitation perceived by the monitored individuals – consequently thermoregulation - may greatly change depending on the habitat type selected (wood, open area, shrubs, etc.).

References

Brivio, F., Grignolio, S., Brogi, R., Benazzi, M., Bertolucci, C., & Apollonio, M. (2017). An analysis of intrinsic and extrinsic factors affecting the activity of a nocturnal species: The wild boar. Mammalian Biology, 84(1), 73e81.

Cahill, S., Llimona, F., Gràcia, J., 2003. Spacing and nocturnal activity of wild boar
Sus scrofa in a mediterranean metropolitan park. Wildl. Biol. 9 (Suppl. 1).

Caley, P., 1997. Movements, activity patterns and habitat use of feral pigs (Sus scrofa) in a Tropical Habitat. Wildl. Res. 24, 77–87.

Gordigiani L, Viviano A, Brivio F, Grignolio S, Lazzeri L, Marcon A, Mori E. (2022) Car2ied away by a moonlight shadow: activity of wild boar in relation to nocturnal light intensity. Mammal Research 67: 39-49.

Grignolio S., Brivio F., Apollonio M., Frigato E., Tettamanti F., Filli F., Bertolucci C. 2018. Is nocturnal activity compensatory in chamois? A study of activity in a cathemeral ungulate. Mamm. Biol. 93: 173–181.

Keuling, O., Stier, N., Roth, M., 2008. How does hunting influence activity and
spatial usage in wild boar Sus scrofa L.? Eur. J. Wildl. Res. 54, 729–737.

Lemel, J., Truve, J., Soderberg, B., 2003. Variation in ranging and activity behaviour
of European wild boar Sus scrofa in Sweden. Wildl. Biol. 9, 29–36.

Montgomery et al. 2020 Animal Behavioral Responses to the COVID-19 Quietus. Trends in Ecology & Evolution 36 (3): 184-186. DOI:https://doi.org/10.1016/j.tree.2020.12.008

Ohashi, H., Saito, M., Horie, R., Tsunoda, H., Noba, H., Ishii, H., Kuwabara, T., Hiroshige, Y., Koike, S., Hoshino, Y., Toda, H., Kaji, K., 2013. Differences in the activity pattern of the wild boar Sus scrofa related to human disturbance. Eur. J. Wildl. Res. 59, 167–177.

Saunders, G., Kay, B., 1991. Movements of feral pigs (Sus scrofa) at sunny corner,
New South Wales. Wildl. Res. 18, 49–61.

The current version of the manuscript represents an improvement over the previous draft. The authors properly addressed most of my previous comments. The description of raw activity data, as well as their processing and analysis, has been satisfactorily elucidated in the revised manuscript. I appreciated the inclusion of circadian activity rhythms in the analysis, which enhances the understanding of wild boar sleeping behaviour. Additionally, I appreciated the new approach used to analysing temperature and night brightness effects.

However, I disagree with the author's decision to exclude aspects related to predation risk and human disturbance from this study. These factors are significant constraints that animals face in natural conditions and could have important effects on the sleep patterns of prey species. As noted by the authors themselves, in a previous study they found that high levels of human presence led to shorter and more frequent sleeping bouts in wild boar. Similar or stronger effects may be expected for the natural predator. While I acknowledge that this is not the primary focus of the study, omitting these important variables could potentially lead to misleading results regarding the effects of other environmental factors. For instance, I wonder if the large inter-and intra-individual variations found in this study might alternatively be explained by the presence of predators and/or human disturbance.

In response to my previous comment, the authors stated that preliminary analyses showed non-significant effects of wolf presence/absence on wild boar sleep, but they opted to exclude this topic from the manuscript. Their reasons for this decision include: i) a binary measure (presence/absence) is considered too coarse for a formal analysis of the predation effect on prey species' sleep; ii) the updated models revealed no effect of the study area (which was initially interpreted as related to predation risk).
While I recognize the challenges in capturing complex ecological interactions in natural conditions, such efforts are crucial when transitioning from experimental/laboratory studies to research on wild animals. On the other hand, the authors propose this study as one of the first examples of research describing sleep in wild and natural conditions. Therefore, I believe that it’s important to attempt to capture the possible constraints that animals face in their natural environment should be done. Furthermore, like myself, other readers may question the potential impact of natural predators. Consequently, I believe that information regarding the presence of predators in one of the study areas should be included in the manuscript. Additionally, I suggest directly incorporating predator presence into the analysis. The variable "study area" may not adequately account for the effect of predator presence, especially considering that wolves were only present in the latter half of the monitoring period (since December 2020, according to the authors).