This night was rather unusual.
The species we encountered behaved differently than they behaved over the last week or over the last couple of weeks (but they did not behave in a wholly atypical manner for their species).
It appeared to me as if something had disrupted their assumed routine and I will describe my observations shortly to provide illustrations for these claims.
However, I thought I would point out that only two significant changes have occurred that might mark a difference between ‘now’ and ‘then’.
On the night between Sunday and Monday (Apr 14 and Apr 15) there was a windstorm.
It was not accompanied by heavy rains but some large trees snapped or were uprooted.
The level of disturbance was comparatively low but it could have altered some habitats, especially, for species that depend on trees or for species who have small home ranges.
Also, temperatures dropped suddenly and sharply (from > 5°C at night over the past weeks to -2 – 0°C last night).
However, the change in temperature was not felt as keenly (at least not until ca. 4 – 5 am when I mostly already ended my observations) because the water and the earth, and such habitats as forests had apparently warmed up enough over the last weeks to counteract the sudden low temperature (although this impacted insect and rodent activity which is relevant).
I have discussed in my previous posts that, according to my observations, sharp fluctuations in temperature tend to bring along hormonal (and possibly otherwise physiological changes and adaptations) disrupting the former metabolic pattern (see Hormonal changes during weather fluctuations).
Thusly, I believe that the sudden drop might have impacted hormonal production in some animals.
It seemed to me that males of these three species (although beaver case is disputable) were affected more greatly than females.
Perhaps once the females have passed from one life cycle stage into another, their hormonal level is governed by the pregnancy/motherhood (beavers and roe deer are currently pregnant while the tawny owls must be incubating/brooding) rather by less impactful changes in temperature (i.e., when fetuses are developing fast or when eggs have been laid, the female might be following her internal hormonal regulations that no longer depend on the climate because climate cues served merely as onset for, e.g., active and fast embryo development).
Meanwhile, the males might be still following the weather fluctuations more closely because their hormonal state is currently (post-mating) affected by climate + by the hormonal state of their mate.
Thus, their behaviour could be a combination of the impacts by abiotic factors + female hormonal state.
Now I shall delve deeper into the observations regarding each species, alphabetically:
Beavers
Over the last two weeks, I had mostly observed the beaver families foraging scattered along their range and there were many lonesome subadults (last year’s kits) coming up with shenanigans while on their own (Beaver observations (end of March, April) – enthused and adventurous youth).
Members of families were seen together more rarely than apart (although they were not far apart from one another but the distance was sufficient and the terrain was divisive enough to claim that they were not foraging together in the same spot).
Tonight all the families I visited (6 or 7) were found close to one another (< 50 metres or < 100 metres in one colony).
I was even fortunate to determine there were two subadults in one of the families (previously, I had thought there was only one).
These were not ‘family picnics’.
Not many trees had been snapped altogether and none had been windfallen in the patches where I observed the family gatherings.
Thereby, the families were not collectively foraging on easily-obtained resources.
It was striking that this phenomenon during the same night was observed in all the families and it was in contrast to the observations over the past weeks.
I wonder what caused this synchronous behaviour.
More precisely, I suppose it was the combination of the storm + drop in temperature that caused it but I wonder through what mechanisms it was brought about.
The temperature as such would not have impacted beavers greatly because, as I mentioned before, the water temperature probably had not changed greatly and while it was colder, some previous nights following much warmer days had felt even cooler due to the evaporation of heat from ground and water (it was chillier due to increased moisture content in the air).
However, it might have impacted the male’s hormonal status (if I am correct to assume that males suffered these fluctuations in a more pronounced manner although this hypothesis will be better discussed in the sections dedicated to roe deer and tawny owls, not beavers because, in beaver families, the group gathering behaviour was not as definitely dominated by the males, i.e., this behaviour was not ‘typical male behaviour’ and it involved all family members).
It is known that rain does not have great effect on beaver foraging behaviout but rain was not the issue during the last storm.
I wonder if the strong winds had forced the family to stay in den for longer.
Thusly, they might sort of have reverted to their winter activity pattern.
Also, it is possible that, after the storm, the male patrolled his territory in order to determine what resources might have been lost and what resources might have become available as well as what foraging/travel routes might have been obstructed.
Such patrolling behaviour is also typical of the period right after ice has melted when territory owners check on their whole range and actively keep out dispersing individuals.
Accordingly, (and also following the sudden and sharp drop in temperature that have altered the male’s hormonal state) the male might have ‘regressed’ into behaviour that is somewhere middle between winter activity pattern and full-blown spring activity pattern (the weather has forced the male to enact late winter/early spring activities but his mate is already quite heavily pregnant which should remind him that it is not winter anymore).
Perhaps the male has thereby also reverted to mate guarding behaviour.
During the period of mating/early pregnancy, I often observed the adult beavers in quite close association (foraging nearby) which I thought could have been concern over the female’s exposure to competitors but alter also predators.
The male might have become ‘confused’ resuming his early spring behaviour and staying close to his mate rather than foraging further along the stream.
The juveniles who have been missing their parents, might have rejoiced in this family reunion sticking close to parents while it is still possible to enjoy their company.
Alternatively, if the beavers were foraging actively last night despite the wind (and as they have probably resumed active growth and development, they could not forego their meals), they might have been tired after struggling against the wind and swimming more turbulent waters.
Even if they were not hanging out in the den, they might have stayed relatively near one another during the storm because the wind would have reduced their ability to send timely warnings on occasion predators were noticed.
There could be other explanations.
Overall, I thought it was important to write down these observations because this change in behaviour was synchronous in the whole population.
Roe deer
Roe deer males have been territorial for a while now but tonight they were especially so.
Typically, I overhear 1 male barking per night (and not during all nights).
I would estimate that I get to hear approximately 1 – 2 barking males per week.
Tonight I heard three males in separate ranges (they were not interacting with one another and their vocalizations were separate events) and they were all barking in rather densely forested patches.
During summer, I cannot say that I observe males more often in closed vs. open habitats but during spring they seem to be patrolling precisely such habitats (see my theory – Roe deer observation (Apr 12, 2024) – my theory of males protecting pregnant females).
Tonight, however, I believe whatever motifs they had had to patrol closed, sheltered habitats before, were added to by territory inspection after the storm.
Roe deer do not have large home ranges and I suspect that a few fallen trees can alter their resource availability, especially, natal site availability for females.
Fallen trees can be of benefit (roe deer can forage on twigs and bark) but they can also obstruct passage (e.g., if they fall criss-cross) impeding travel and destroying potential shelters.
On the other hand, fallen trees could also provide shelter because visibility near them is low.
While ungulates do not prefer to forage near coarse woody debris (impaired vigilance against predators), their young might perhaps use fallen logs to for hiding and in some opening taller herbaceous species might grow also offering hiding spots.
These changes might be apprehended by the territorial male upon inspection.
However, I also suspect that trespassing rates might be higher after storm (due to some spooked dispersing deer seeking shelter or becoming lost once the landscape has changed or due to curiosity by the neighbours who perhaps visited these areas during winter and who would like to discover what has changed after they have inspected their own ranges).
My suspicion is based on the fact that these males were patrolling at ca. 1 am – 4 am.
Their ranges are not that large and roe deer in this region are active during day and also during afternoon, evening hours.
The males would have had enough time to explore their own territories before 1 am – 4 am.
Perhaps, however, after they have explored their own territories, they have to make sure that nobody else is exploring their territories as they themselves might feel inclined to catch a glimpse in the neighbouring ranges.
Such species as roe deer who tend to spend all their lives in one range which is not that big might memorize their range in a rather detailed manner.
Therefore, they might also be able to appreciate any modifications to their range noticing minor alterations.
Thus, it is possible that the males were still inspecting their own ranges even more than half a day after the storm event (especially, because they also had to feed at some point and to rest).
One of the males was rather different in his vocalizations than the others.
I recognized this individual from a former observation (Roe deer observation (Apr 3, 2024) – territorial conflict) and I realize now that this male might have a slightly different voice than average roe deer males.
His voice is not as guttural and resonant.
The male’s vocalization tonight was also rather unique (I had never heard such vocalization before).
Normally, roe deer bark and the energy is invested in the bark itself.
The bark then resonates making each sound appear longer.
This male apparently could not invest in the bark itself and he seemed to have adapted by actively (and somewhat strenuously) extending the duration of the bark itself.
Namely, the duration of his bark was not achieved through the impact of the loud initial sound which then reverberated (in which case, the actively produced sound is short but intense).
Instead he was actively producing long barks that were not as intense overall but in which he invested throughout the stages of the bark itself and its aftereffect.
That is to say, where other males would have ceased the vocalizations enjoying their prolonged resonance in which they invested no longer, this male had to invest both in the initial bark and in its continuation (he was making effort all through the sound sequence).
However, I have also heard this male barking sharply (if not resonantly) before, and it appeared to me that the vocalization was perhaps different also in its message.
I think that when this male is patrolling his territory, he is probably also producing vocalizations that are different from typical roe deer male vocalizations.
But I am not certain that the ‘strangeness’ of his vocalizations tonight were only due to his unique vocals.
I suspect that his vocalizations were not identical in their intent to other males’ vocalizations.
They did not sound very threatening.
In fact, even the defensive bark I have heard from him previously was more intimidating than these vocalizations.
I have sometimes observed roe deer males who were seemingly ‘talking to themselves’ and also males who were sort of talking to the female because I knew that there was a female nearby where they were barking.
I wonder if this male was communicating with a female rather than a male.
I have never seen scientific publications in which roe deer male vocalizations of the louder type would have been discussed as communication tools in his interactions with females rather than with other males.
I suppose I should address this issue in another post.
For now, I will state that I believe this male was communicating something different than the other males and that he perhaps was discussing their new situation with the female on his range.
Interestingly, the roe deer males did not seem to have reverted to some ‘earlier stage’ in the seasonal activity patterns (unlike perhaps beavers and tawny owls).
Perhaps it is because roe deer females are income breeders, i.e., their reproductive activity is more closely linked to current resource availability than to resources they have gathered over longer periods storing them as their own body reserves.
Thus, it is possible that, while in other species, the reproductive development and the hormonal levels follow a more gradual path, related to long-term climate patterns, photoperiod etc. rather than predominantly tracking the present-time resource availability, in roe deer species, females can seriously upstart their pregnancy rate once resources have become more plentiful.
Their reproductive development might be accelerated in years when the weather has warmed early and suddenly while capital breeders and species which rely on evolutionary traditions (such as beavers) cannot adjust as flexibly and their pregnancy occurs rather according to physiological mechanisms developed over thousands and millions of years than according to year-to-year variation.
Therefore, the roe deer females might have jumped into their spring hormonal rates in a more pronounced manner and the males might be affected by their hormonal status greatly enough to mitigate the impacts of fluctuating weather.
Tawny owls
Tawny owls used to be highly vocal during March and early April but, over the last week, they grew quieter which I attributed to chicks having hatched and males having less time to invest in activities other than hunting in order to provide for their chicks and their mate.
Tonight the tawny owls began hooting at about 2 am and did not stop until about 4 am.
Additionally, both neighbouring males were actively flying over their territories and hooting until, eventually, they each located themselves near their respective nests and hooted from there.
Previously, I had never even heard the neighbouring males interacting in such manner.
While I did not overhear anything suggestive of a conflict and at no point did one of the males seem to have intruded in the other male’s territory, they seemed to communicating also with each other (at least, toward the end of my observation) or at least they were highly aware of one another because sometimes their vocalizations were synchronized.
They responded to one another’s vocalizations.
As I mentioned early in the post, invertebrates and rodents were less active tonight.
Perhaps the tawny owls were having a harder time catching prey and, therefore, they could spare a moment for vocalizations once again (because hunting effort requires energy which must be followed by rest regardless of the actual success).
I also wonder if they used the vocalizations to spook out any rodents.
They were both flying and hooting intensely.
Perhaps they were, too, surveying the after-storm status of their territory.
Uprooted trees might have exposed some rodent burrows or created gaps in the canopy allowing to search for prey there.
However, I thought that the intense hooting might have stirred some of their prey species (it was very stirring even for me and I am not tawny owl prey) who, despite the cold weather, might have become anxious as to the meaning of this ruckus and they might have peeked out of their burrows to make sure all was safe (which would make it unsafe for them).
The tawny owls might hoot and then listen in for rodent activity (assumed in response to their hooting).
Eventually, as the males settled each near their nest (and their nests were situated about 1 km apart), they kept calling out to one another.
It was almost as a long-distance conversation between neighbours who had just estimated the situation on their property after storm and they were exchanging some comments, concerns and hopes.
There was really no hostility to their vocalizations and as they were synchronizing, it was almost as if they were comparing notes, seeing if they could ‘speak on the same level’ or if their status had somehow considerably changed respective to that of their neighbours.
For example, if one male had experienced higher anxiety than the other due to what he had witnessed after the storm, he might not have been able to adjust his vocalizations to the calmer hooting by his neighbour.
Of course, I am aware that tawny owls are some of the most aggressive birds of prey who are territorial to death.
Still, I stand by my interpretation that these neighbours were not engaged in a hostile display.
However, the intense vocalizations and all the flying around surveying one’s range could have resulted in a ‘regression’ to earlier stages in the nesting cycle whereby the pair defends their territory and their nest against other claimants (before their clutch has been laid).
The landing near the nest and vocalizing as such could have been remnants of such behaviour brought about by a combination of hormonal adjustments by the male during the sudden drop in temperature as well as the aftermath of the storm which resulted in behaviours reminiscent of their February, March activities.
However, as the male realized that his mate was already in the nest with eggs/chicks and as he heard that the neighbouring male was also near his nest where he, too, had a mate and eggs/chicks, the tawny owl male might have come by some relief that the reproductive cycle has proceeded far enough for other tawny owls to be a threat to him (there are not that many large cavity-nesting competitors for tawny owls here and conspecifics are probably the main competitors to one another with regard to nesting sites and territories).
The males might have even helped one another to calm down after the upset caused by altered hormonal state + lack of prey (which is worrisome for the responsible family provider).
***
Thus, I suppose that these altered behaviours were the result of the combination of the storm followed by the huge drop in temperature.
Perhaps had it been simply the storm or the drop in temperature, the effects would have not been as dramatic on the species’ behaviour but the storm caused some activities that might have triggered physiological responses due to the similarity of the behaviours conducted during/after the storm and the behaviours carried out earlier in winter/spring.
***
On the following night (Apr 16/17), the activity was intermediate and much calmed.
Some beaver families were found together but there were also family members foraging in a scattered manner and we encountered some ‘forlorn’ youngsters, as well.
I heard one roe deer male.
Tawny owls were quiet until 4.30 am when one male (mentioned above) briefly vocalized near his family nest.
However, I have noticed that nearing dawn (during civil twilight) tawny owls often hoot near the nest perhaps to ‘wrap up’ their nightly routines.
Rodent activity was more notable tonight although it was still rather cold (ca. -1 °C) and it felt colder, too, compared to the previous night.
Notes by Ieva 